That is wonderful and you can see that she is starting to come out of her shell.
I am not sure if I would be real concerned about Gizmo playing with her unless I saw how she reacts to him when I was home. Does she get mad? Does she run into her safe haven? Does she tell him off from time to time? Was she with other dogs in the kennel so she is comfortable with him? Most puppies will tolerate a lot from each other and if she is not reacting I think she is fine but you will have to look into her eyes to see if she is frightened by his attention.
My gang thinks topknots were created for them to haul each other around
. I find even my 3# little girl Bella can take care of herself when she has had enough. Again, all of my dogs were rescue except for one and they have all adjusted to each other given time, patience and love.