I have never taken naltrexone or had an implant. I have heard, though, that the implant is for MOTIVATED addicts. There is a risk of overdose if an addict tries to use enough to override the block. I've read stories about this, but have no first hand knowledge. But I did want to raise this issue. I think it's important to get all the facts and that your daughter is aware of the consequences of using on top of naltrexone.
I wish the best for you and your daughter!