How do I help my friend with bpd without overstepping or triggering them?

Hello, I have a question. I know a little bit about bpd but not as much as I should. I’m wanting to know more about it and more about ways I can support people with it.

My good friend who is 17 is diagnosed with bpd and as you may understand has episodes. They can get really bad and send them into a dark place for a long time. I love them very much, I want to spend time with them and get them out of the house to try and help them feel better but when they’re in an episode they can’t really do much.

They cancel plans sometimes when they’re having a hard time and I just want to know ways I can help them without triggering them and making them more anxious. I would never blame then, and I can understand how they feel to a point but I’m not struggling with bpd, so I’m not really sure how to get them out of the house or just go over for a visit to cheer them up, so I was wondering what I can do as a friend to help? I hope this question isn’t worded in a way to offend anybody, I just want to help my friend and see them more