I think with Narcissists (assuming that is what your MIL is) they have this Cognitive dissonance between:

1) I am supposed to give gifts in this situation. To not give gifts looks bad.
2) I am the bestest person in the whole wide world! I should be getting the gifts! Or at least the BEST gifts.

How to resolve this?

Narcissists do this in various ways.

1) Gatekeeper....if others send the presents to ME, then it is like I have sent you presents but I didn't have to pay for them.

2) Inferior/Cheap presents: I got you a present...so what if it is crap. It is the thought that counts.

3) Message presents: I got you a present...so it is a small even though you wear large? Well you should lose weight.

4) Power presents: You went no contact? Well I am a grandma and am allowed to send presents at Christmas!

5) Attempted presents: Well I tried to get you a present with my superior discount card because I am the BEST at bargains, but oh well, the store wouldn't sell them to me RIGHT NOW! Not my fault.

6)Revenge Lack of Presents: Well you didn't (send me anything/call me on time/whatever) so I am not going to send you a present...I would have, of course, if only you didn't (whatever)