Website: It looks like the creator just slapped on a Smack Jeeves template and called it a day. I'm aware that it's just a short story, so it might not be worthy of a robust site design, but I still expect at least some sort of a personal touch.
The creator completed the story about five-and-a-half months after the cover was posted, and she deserves some credit for sticking with the project and getting through it promptly. So many creators abandon their projects after posting just a few pages, or even after just posting a cover, that I can't help but view completing this story as a accomplishment.
Lastly, Page 17's too big for the layout, which makes it extend past the main column. This problem could easily be fixed by making the image about 25 percent smaller.
Writing: The problem with having children as the main characters of a story's that children just aren't that interesting. Capable writers will generally get around this by having young characters act more mature than they normally would, instead occupying a gray area between childhood and adulthood. This technique's particularly effective with younger audiences, who are attracted to portrayals of children as being important and independent. The creator of Anabel and Her Sister's clearly still getting the hang of writing, though, which is why she chose to portray the children in the story as petty, bickering juveniles. It might be more realistic than a typical story, but it's abrasive and tedious, and the more the children teased each other, the more impatient I got for the story to be over.
The plot seems to revolve around an "I see dead people" concept like in The Sixth Sense, but the mechanics of it get lost in the characters' immaturity. Particularly, the story gets too wrapped up in the love/hate relationship between Anabel and Robert, and it couldn't get me to care enough about the secret crush of a girl who appears to be about 10 years old and probably acts younger than that. It also doesn't help that all of the characters are annoying and boring, which makes the idea of trying to dissect the confusing plot a lot less appealing. One part did come across as clever, though, which is when Anabel considers helping the stranger kidnap her so that she can get away from the haunted house. It was successful in catching me off-guard, although I would've preferred it if that situation had been developed more.
There are a lot of spelling and grammatical issues, which makes the webcomic harder to read. The most obvious of these is that the creator often capitalizes normal words, apparently to add emphasis, when bolding or underlining the text would look more natural. The letter "P" also often looks capitalized for normal words, and while it could be an issue with the creator's handwriting, it's impossible to ignore when other words are being inappropriately capitalized as well. The spelling errors include "noisey" on Page 3, "tounge" on Page 6, "breath" (instead of "breathe") on Page 15, and "good ridance" (instead of "good riddance") on Page 28, while Pages 15 and 24 are missing apostrophes; a 31-page story shouldn't have this many mistakes. The most significant grammatical problem is with the story's title, though, which is written three different ways: as "Anabel & Her Sister" on the cover, as "Anabel and her Sister" on the website, and as "Anabel and Her sister" on the comic's banner. I understand that the creator isn't an expert at grammar, but being inconsistent with the story's title is just carelessness.
Art: Perspectives are a major problem here. I somewhat appreciate that the creator's at least attempting them; however, they're so wildly off that I actually started to feel disoriented reading the comic. As seen in the examples here, here, and here, the creator clearly has only a minimal understanding of one-point perspective. I recommend that she does some focused practice on the subject, possibly trying things like drawing rows of buildings or a room full of blocks. Another area causing issues here is the line-width variation. Lines in the foreground need to be thicker than lines in the background, and the creator either uses the same thickness for all the lines (like here and here), or, even worse, makes the lines in the background thicker than those in the foreground (like here). Doing this wrong creates a distorted look, making it confusing what the spatial relationship is between various people and objects.
The anatomy's generally weak, with noses, ears, and hands being particularly problematic areas. With noses, the creator draws them front-on as either a vertical line, a slightly curved line, or a "button" nose, and she never seems to reach a level of comfort or consistency with them. Ears are done inconsistently, and often are too long (like elf ears) and almost parallel to the jawline. And hands often get drawn way too small, like about the size of the character's mouth, and frequently look sloppy, like on this page, where the second panel has thin, spiky fingers and the third panel only has four fingers. The characters are also almost never drawn with clavicles, which are physically prominent enough to be shown even in a cartoony style like this. Lastly, Anabel's dress is drawn in a minimalistic manner, with the lower half usually shown as a long, solid object that gets cut off around the ankles. The creator should study how loose clothing like that moves and folds around the limbs of the person wearing it.
All of the pages have a problem that's common in webcomics, which is that there are too many "generic" shots, which would be close shots, and figures that are either shown front-on or in profile. This weakness is probably the most obvious in this page, where Anabel's head's drawn in profile while her body's drawn at an angle. A more natural way to draw Anabel in that situation would be to show the edge of her face, with the tip of her nose slightly visible beyond the outline. A particular consequence of not having more wide shots is that the setting's Victorian architecture and objects don't get shown as much as they should be. The characters seem to live in a haunted mansion, and it would've been great to have a detailed shot of its exterior at some point, but it's only ever seen as a small object in the distance.
I have a bit of praise for the artwork, which is that the creator's somewhat competent at doing a moody noir style. Starting with Page 14, she starts using more contrast, and this aspect becomes more prominent until Page 20, when the story switches to a gray, washed-out look. Those seven noir-ish pages are the strongest part of the story, and the creator should consider developing this style further.
Overall: Reading Anabel and Her Sister, I was reminded of what Simon Cowell said when the infamous William Hung bombed on American Idol: "You can't sing. You can't dance. What do you want me to say?" Well, this creator can't write, and she can't draw, and I don't have any reservations about giving her webcomic a lousy grade. However, it's clear to me that she's still a beginner-level webcartoonist, and she has plenty of room to improve if she chooses to do so.