Hello BPD forum

My friend of several years has BPD and anxiety is very in-the-moment and impulsive.
I am trying to understand why my friend with BPD can often be so pleasantly intense and close while with me or my friends and appear keen to be involved in activities.
But in between our meetings, they are Distant.
I can feel let down when they do not stick to what we agreed to.
It is like speaking to a different person when I phone to find out where they are. They have lost all the enthusiasm they had when we met in person.

Distant: for example, they limit the length of time and number of meetings with others. When invited, they often want to stay at home on their own. They only seem to want to interact in person. They do not reply to simple messages, including when helped, but acknowledge received if asked. While in person, they appear overly keen and say they enjoy the company and should do it again soon. Their words often do not hold once they leave. I have done some reading on BPD.

Is this Distant behaviour likely a protection mechanism from becoming overly attached to people?

I would have thought my friend's intense and close interactions with people could increase their chance of becoming attached?
If they do not want to get attached to others, their way of interacting would strangely work against them?

I guess due to BPD, they like or have little control over this intense and close way of interacting?

Pat