Hi J.,
I have only read a couple of the other responses, but didn't see anything about a shower. (there may have been, but I didn't read all of them)
My oldest, now 18 and in college, like playing in the bath for a while before I washed her and her hair. Then one day, she didn't like it anymore - I did the same as some moms - didn't wash her hair everytime. Then one day, she wanted to take a shower with me, so I let her in and was able to wash her up without problem.
She started liking baths again when my 2nd was born and she had someone to play with (when baby was about 6 months old). She loved her baby.
My youngest, will be 3 this month, still takes showers with me. It is much easier to get her washed, she has alot of hair! She likes her bath, once or twice a week, but its showers that she likes most. She has been taking showers with me since she could sit up on her own.
I had to pick her up and put her head and parts of her body under the water to rinse, but also let her play with it with her hands -so she knows it wont hurt.
good luck
Another thought - do you have rough non slip stickers on the bottom of your tub? they may hurt her sensitive skin when she sits down?