This is a difficult question.. Because a lot of these things are natural. Everyone will have had a big argument and fallen out with someone in the past and drifting apart is kind of a fact of life. For me I think how you deal with these things is more of a pointer to bpd.
For instance instead of ignoring someone after a huge row I will actually pester them or try and start the argument again, or do the opposite and profusely apologise and not let it go until they forgive me. The feeling of drifting apart from people also goes one of two ways, either I will become extremely depressed and feel abandoned by them personally even if it's a gradual process and something they nor I have any control over... The other way is i completely cut them off like you said, i do this to avoid the pain...

A lot of the time I will avoid casual friendships, i have my absolute best friends and my family, the rest of the world I keep at arms length so that they cannot make me feel this way. Certain people have slipped through that net though and I have become attached, this always ends badly.

My point is, it's not abnormal for anyone to make friends and break friends and drift apart, it's the effect that has on you, how you react and what you do in future as a result of these things, also maybe If it seems to be a repeating pattern of the same situation happening over and over.

Hope this helps