<human>: My sister spent the weekend with my boyfriend and I. They have met multiple times over the past few years and have always got along. I was really enjoying all of our time together until she started flirting more and more with him. She kept making a point to touch him and 'accidentally' flashed him more than once. He played along with her, laughing and smiling, but never provoked her or touched her back, although he didn't seem uncomfortable. 

I'm not sure if I'm making this a huge deal in my head or not. I didn't say anything to my sister because I don't want to start a fight with someone I see as one of my best friends. She has not behaved like this in the past, so perhaps she really didn't mean anything. Then again, I feel extremely shitty every time I think about it and don't want to talk to her for a while. Am I overreacting? Should I say something to her?

Can you give me a shortened version of the text?
<bot>: Sister was flirting with my boyfriend a lot. I feel like I'm overreacting to her actions, but I feel very hurt and betrayed. Best way to handle this?