She sounds very...special.
I think it really depends on your relationship with her.
If shes a distant in-law that you dont really have much to do with. Then let you DH deal with her
If you want to keep them you can either be blunt and say "no i paid for them" or you can lie and say you gave/sold them to a friend who really needed them.
Or you can simply ignore her and go about your normal business.