Does this sound appropriate? (interaction with a student teacher)?

That's the sad part about having a great teacher who was also a friend.Eventually you have to move on.Reality does not allow time for that.Remember her for what she gave you and wish her luck in her future.If she offers to keep in touch then you can give her your email,Otherwise thank her for being there and end it just like that.She will remember you but life goes on.Good luck and let go of one and God will give you another.