Mystery Snails are awesome! :D However, if you already know your girl is aggressive I would be hesitant about putting any tankmates in with her. Snails have antennae which can look like worms to some fish, and may be bitten off (they will grow back, but it's not pleasant for the snail, especially if it happens continuously). They will eat pretty much anything dead, as well as sinking pellets. In my opinion algae wafers are the best things to feed them; my snail Gary noms on them like crazy! But anyways, that's just my two cents on the subject. :)
Kindness and respect should be shown to all animals, no matter if they are furry, scaly, big, or small. Be a hero to the animals and GO VEGAN!