Even though she bought you the frivolous things that your parents either could not afford or thought were a waste of money with the little money she earned, she never had anyone do that for her and might not know how to accept it.
Everyone has different needs and wants, so maybe you can explain to her that you love her very much and want to take some of the stress off of her. Ask her what that would be. Say you would love to have her join you for even some of Pesach, but if that makes her uncomfortable you would like to do something else. Then say something like, “What can I do to reduce your pre-Pesach stress?” Perhaps you can help her in other ways – sending her extra cleaning help or for a post-Pesach massage.
I hope these ideas have been helpful! Hatzlocha!