BPDFamily.com

Mom, hypothesized BPD by my therapist, late 80s
Dad, early 90s, not BPD, sweet, kind, hen-pecked
Siblings and me - our 60s
Grandchildren - 30s
Great-grandchildren - we're still waiting
We have a no gifts between adults (which is really the oldest two geneartions) agreement which makes sense.
But, I love making cookies and treats, so I bring them to the family celebration.  I am the only one who lives in a different town, less than three hours away.
Weekend before Christmas, I brought a sample of the treats to my Mom's house.  Dad got in trouble for eating too much of it.

Christmas, I brought most everything there.  I make a lot of different things, knowing what special things different people like - nieces/nephews, my siblings, and my parents.  I made the mistake of taking it all to my Mother's kitchen and letting the others come get what they wanted.  Dad told me at the end of Christmas that when he went to get the special thing that I made for him, it was almost all gone.  I had heard my Mom telling my sister "take all of that, we don't eat it".  I didn't know at the time what item she was talking about.  But there was an dish at Thanksgiving and a dish at Christmas that were prepared by the cooks with him in mind and Mom gave those things away too. 

I un-grinched her over the weekend.  I made another batch of his favorite and boxed it up. I also created a box of the other item he got in trouble for eating too much of a week before.  I went back for a third visit over the weekend.  I put the items in his car in the garage and sent him a phone text (yes, at 90, he texts!) telling him that there was a surprise for him in his car and to go get it when he could get it without being seen.

They do have separate rooms.  She won't step foot into his, and he barely comes out of it.  Still, if she finds out, we will both get the wrath of grinch mom, unfortunately, him  more than me.

I see some parallels to my parents and situation at their ages.

There are long standing dynamics between your parents- and likely your father has been in the role of emotional caretaker/rescuer for BPD mother. BPD mother's feelings were the central focus of the family.

Dad getting older, and, eventually having physical issues, shifted the dynamics to where attention was on him. In a "normal" situation, your mother would also be more attentive to him but the reaction from BPD mother was the opposite. With less attention to her, her BPD behavior escalated.

If I brought a treat for my father, BPD mother would be angry that I brought food in without her permission, or even discard it. This is similar to your mother giving your treat for your dad to your sister and being angry at him for eating too much of it.

I think what is driving your mother's behavior is the shift in dynamics and her feelings. Being controlling is a way of managing anxiety. What is happening- and is difficult for everyone in the family to see is that Dad is aging, and you all have feelings about this. For pwBPD- they perceive their feelings as being external to them- someone or something is "doing this to them" and so they get angry and act out.

We also brought treats in for  Dad on the sly too and unfortunately, if BPD mother found out, she'd be angry.

I understand your intentions and wanting to make Christmas special for Dad. Be aware of the Karpman triangle dynamics when you do this. Your Dad has likely been in Rescuer mode to your mother who has been in "Victim" mode. If you step in as Rescuer to Dad, BPD mother may perceive that as an attack (Pesecutor) on her, take Victim perspective and Dad may align with her as Rescuer with you in Persecutor position.

It's great that your father texts with you. Be careful what you say to him. Any emails, phone calls, texts with Dad were potentially shared with BPD mother. Text as if she could read them too.

But don't let any of this stop you from doing nice things for your father, making goodies for him, and keeping your connection with him. Just remain aware of the possible reactions so you don't react emotionally to them. Dad knows you made the treats, even if he doesn't get them- that's on your mother, not you. The Grinch may be able to take the cookies away from Christmas but not the spirit of it, or your love for your Dad. You did a good thing and how she reacted doesn't change that.