My girlfriend has played the hell out of CakeMania and Cookingmama and wants new games, but her tastes are specific. And trying to find reviews of casual games that aren't written by people who have a natural disdain for them is kind of difficult. So is there a website devoted to helping the "non-gamer" get their game on?

Right now we're looking at either Mysims, Sims 2 DS or who the hell else knows what. 

The only sites I've seen even have good reviews of casual games are generally Nintendo centric, but even then they're not all for the games, but a site that is all about casual games, I've never found this to be honest.

My Sims is pretty good though, Sims 2 DS is just kinda eh to me. To each their own though.

Look up those games you mentioned she likes on metacritic, and then look at the links to full reveiws of that have about the score you would expect for the game. That will tell you what sites score them how you would want them scored. (Assuming the review itself is also matches her experience).

Mysims is very good for the DS. Similar to Animal Crossing but the town is much more bigger.

My sister is also a gamer, more casual, so I'll just list the games she borrows me sometimes (thus, my DS disappears for quite some time)

- New Super Mario Bros
- Brain Trainning
- Big Bang Mini
- Tetris
- Soul Bubbles (still not getting what possesses her in this game)
- N-plus

And about the website. I don't know.

Maybe try:
http://www.whattheyplay.com/

The official Nintendo Magazine in the UK (ONM) is good for casual reviews. Quite a few people don't like the mag because they are too generous towards them. The website is: http://www.officialnintendomagazine.co.uk/reviews.php . They put quite a few reviews up on there but because it's a magazine I dont think everything is up on there. At least its something :)