This is all about respect for other people.
Whether you are involved with them or no longer involved with them.
Whether you like the person or not.
It is not about getting rid of them before you get together with someone else.
It is not about shared memories like the pictures taken of the two of you in DisneyWorld.
These pics were taken i(I am assuming) during private moments between the two of you. There was an underlying trust that was involved in taking and keeping these pictures that had it basis in your relationship.
Now that the relationship (the way it was) is no longer there that underlying trust and connection between the two of you, that ensures that these pics remain private, that formed the basis of your realtionship is no longer there.
She asked you to delete them.
Becuase you still have some relationship with her the decision should be easy. You do as she asks.
I could understand if there was some sort of animosity that you would not want to do as she asked but then, that is the reason she does not want you to have them anymore.
Would I get rid of them? Now that is a completely diffeent story.
Just kidding, I hope that I would be able to do as asked but I can't say for sure.