What if 3 questions don’t work?

Brooke, I need your advice.
I tired to help my mom to put in order her wardrobe and 3 questions didn’t work at all, she always finds a reason not to throw away a thing. She gives a lot of hypothetical reasons why she’ll need this item in boundless future. For example, there’s an old but very warm fur coat she has not been wearing for more than 20 years, and the size doesn’t fit her, and the coat is to heavy for her. She definitely won’t wear this coat again. But she says that it might be an extraordinary cold winter in some future, when this coat may help. The other argument is that she spent money to buy this or that thing. But now it’s a crap nobody desires to buy. She is a stubborn to get rid of clothes or other things, no matter if it’s outdated or she hasn’t been using it anymore for 2-20…years! She refuses to follow the rule that if one of 3 answers is No – it’s better to not to keep this thing.
I feel in some way she refuses to throw away items because of a thought that we throw away a part of her life or her personality. I don’t know how to help her to change her mind. What do you advise in this situation?
I would also like to know how to deal with similar situation with a client, not mom? How do you deal with Very stubborn clients?
Thank you!

Regards, Vita.