Normally, I would say leave her, if it's not interfering with sleep at home.
If it's really getting in the way of your afternoon routine, though, I would let her sleep as long as you can, but wake her when you have to.
What is she like when she is tired? Can you put her down a little earlier? That way she still gets the big nap that she apparently needs?
Just curious; mom says she goes down ok, but is she wakeful at night?