Hi notdefeated
Welcome.
It's difficult and painful for one to have a partner admitted to a facility based on what you've shared. Sometimes, when people are recovering from something like this, one of the best things they can do for themselves is to recognise that they're in a process to help themselves. I encourage you to see the two of you as distinct people with distinct needs—even though I know living with a pwBPD can feel quite like you're the same person.
Yes, I understand that dysfunction may cause you to guess your feelings of love for each other. Her BPD is part of her personality, but that doesn't mean that there isn't love. I hope you'll continue to read more, but with an additional dose of compassion for her, and for you.
You expressed that you'd like to support her. One way the partner can support the pwBPD is through communicating well. Here's a good place to start:
https://bpdfamily.com/content/communication-skills-dont-be-invalidatingI hope to hear more of how your story develops.