I would say something like "My dear friend, everytime I see these pieces of jewelry I cant help but to think of you. It brings me such joy to see your face when you open them (see them). Please you don't need to pay back the favor. Seeing your smile is all I need."
I've been giving a financially poor friend costume jewelry. Now she has started buying me gifts that cost a lot. She doesn't have that kind of money. How can I tell her to she doesn't need to do this??
This is a gift from the heart,
receive it the same way.
if you REALLY REALLY don't want them giving it to you, let them know how much you appreciate their gift but how hard it is for you to receive it, considering her financial situation. If she/he continues to give you these gifts, you should really be very firm and tell her how you feel when she gives you the gifts. After that, you probably can't do much else to stop her.