Ive worked in paediatrics at points in my career, and it is entirely normal and a healthy expression of developing sexuality. I think boundaries, as you have been doing, are a good idea and usually children learn to regulate themselves. I really recomend that you read a book called pleasure: the truth about female sexuality by margaret leroy. it will help you reconcile a lot of what is going on with your own feelings towards your daughter.It is easily obtainable on Amazon.