I accidentally stole an iron dagger from Anise's Cabin in her cottage near Riverwood and then I had to fight her and kill her. Are there any quests I may have missed out on?
Anise's Cabin is not used in any quest lines that I, or this page are aware of. There's a letter to Anise, an Alchemy skill book, an Alchemy Lab and an Arcane Enchanter in the basement, a bed and a garden. That's it. No quests reference it, everything in the house is considered stolen if you take it. Just an oddball little hut in the middle of nowhere.
No, if you go in her secret annex at the back of her house and come out, she will attack you. She has no pourpose, she is just a random encounter.