What is it you want her to do?
When I send Ghillie out for a retrieve he comes back in with it, at which point I am squatting down with arms held out for him to come into, he sits at my feet and I tell him "Good lad" give him a quick stroke and take the retrieve off him saying "Dead" take it out of sight, put it behind my back, in a pocket or game bag. i don't do too many as he gets bored of them and will mess about.
To get him to hold it I use to put the dummy in his mouth, scratch under his chin and say "Hold, hold" not for too long, and then praise him.
Do you leave Rhian's toys around for her to play with?
Ghillie has Kongs in his run and tennis balls and dummies for training, if left with a tennis ball he will strip it

If he does start to chew on a dummy or ball whist training I use a gruff voice and stop him straight away and remove it.
With picking up the retrieve some times they need to readjust to get a better grip, i know Ghillie does with game or Dokken's some times.
Hope this helps