OK, if someone avoided me for any reason, the first thing I would come up with is, maybe it's them, maybe they are abnormal somehow. Not.

I would allow myself to feel hurt by being excluded. Then I would probably not be chitty chatty with that person if I'm just their second choice. Then I would rather read a book or something.

Finally I would accept they simply don't like me, but then they can't have my friendship when it is convenient for them either.