Something other than Prozac?

What is another drug that can be taken instead of Prozac? My g/f has been on Prozac for almost 11 years (since she was 19, she is now 30). Her dosages have gone up and down over the years and she has been taking 60mg (her highest dosage ever) for the past 6 months and it still doesn't seem to be working as well as it used to. Has her body built up some kind of immunity to this drug since she's been taking it so long? Is there something else (a different drug) she can talk to her doctor about? There has been alot of stress over the past few months as we're trying to get our house sold and buy another one, do you think once the stress is less her meds will work better again? Thanks so much