My son is 3.5 also and in the same situation. I would say to try showing other kids her age on the potty. That helped in the beginning but now he's comfy doing his business in the potty. However, it might work for you too!
My daughter is 4 and is still having a very hard time with potty training.. I've tried rewards, I've tried the underwear trick, nothing has worked.. She does tell me when she has to go at times, but she doesn't do it often...
My son is 3.5 also and in the same situation. I would say to try showing other kids her age on the potty. That helped in the beginning but now he's comfy doing his business in the potty. However, it might work for you too!