I think jewelry is a little different than clothing. Unless the clothing was actually the ex's clothing. Like, I'm not gonna go around wearing my ex's button down shirt around the house.
I'd say if it's just costume stuff, then no worries, but anything with value - monetary or otherwise should probably not really be something she should wear.
"In most of our human relationships, we spend much of our time reassuring one another that our costumes of identity are on straight."
— Ram Dass