Need opinions about Diamond Jewelry

I thought by posting on this board vs. the OT, I would received more serious responses and advice.

My sister's engagement ring was purchased locally from a reputable jeweler 3.5 years ago. After initial resizing of the ring, one of her pave diamond stones fell out and was replaced by the jeweler. Recently, she had a 2nd stone fall out (not the same stone) which was also replaced. She goes back to the jeweler and requests the 2 previous stones that were replaced be replaced again because the original replacement stones were noticeably smaller and different from the rest of the band. After getting her ring back again, she notices a 3rd stone has fallen out. She went speak to the jeweler again yesterday and he basically said that this was just going to happen with this type of pave band and he would continue replacing the stones.

She works at a hospital and does not wear her engagement ring to work in fear of messing it up and when she gets home she puts it in her jewelry box. After explaining this to the jeweler, he said she should be able to do whatever she wanted including "playing basketball" with the ring on without problems because it should be durable. So, at this point is considering an entire new band for her center stone, as continuously having to deal with this issue is getting old. Should the jeweler be responsible for replacing the band or should she be responsible for paying for a new one?

Any advice appreciated, thanks in advance.