<human>: Can you condense the text into three sentences or less?

I had a group of friends that dropped a bomb on me a few days ago: I didn't fit in the group and it would be better that I never show up again. I saw that one coming because they were pushing me out for a few months now. Questions about what was going on were always avoided, until now. I feel horrible. (Big group, lost around 10-20 friends in just one evening.)

I have a hard time understanding what to do now. I am friendless. I do have 1 very close friend left, but he isn't always around because of college. I have no plans left for the summer, except study for a few re-examinations.

My sister knows this and invited me to do a few trips together with her and her boyfriend. I don't want to burden her with this. I don't want her to pity me. It reminds me of when I wanted to go to the fair but I couldn't find any friends to go with. My sister toke me along as well. I felt bad for her that she couldn't enjoy this alone with her boyfriend.

So, what should I do? Am I correct to politely decline her offer? She did seem to be kind of offended, or worried that she offended me. Or should I take the offer and make the best of my summer vacation?

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<bot>: I'm going through a bad time. Sister wants to take me along to various trips, but I don't want to burden her with my problems. What should I do?