MIL and Shopping Addiction?

Has anyone ever dealt with a family member who has a shopping addiction? My MIL is constantly in debt due to obsessive shopping for things that aren’t needed (both for herself and others) because she thinks she’s getting a good deal.

Case in point - my husband and I have FOUR coffee makers and he doesn’t drink coffee (one 2 cup, one 14 cup, one catering size and a Nespresso Machine - yes I realize this is excessive but they were gifts and we do use them for different circumstances). My MIL has decided that none of the four make good enough coffee for her family and bought another one to use during their visit at Christmas because she had Kohl’s cash she needed to use (and still spent $70 after all her discounts). This is just the latest example, as this has been going on as long as I’ve known her (10 years). It puts such a strain on our relationship as I often try to decline gifts knowing it’s not something we’ll use and she went way over what she can afford.

It’s starting to really get to my husband too as anytime he’s tried to bring it up with her she’s absolutely blown up/yelled screamed and cried about it. I know denial is a part of addict behavior, but it seems like no one takes this one seriously. She’s straining her relationships with her kids and sending her finances spiraling and I’m really concerned for her if something doesn’t change. Christmas used to be my favorite holiday, and we’ve got a little one on the way I’m so excited to have her experience that magic, but lately it’s been the WORST holiday as a result of this.

She is on medication for depression, but I’m not sure how well it’s monitored as i think she only goes in every 6 months to a year to talk with someone (and I’ve noticed her have pretty significant swings without discussing with a dr).

So long story short, how do you carefully help a loved one get through an addiction so many people believe doesn’t exist?