I suspect my sister-in-law's best friend is flirting with my husband, and my SIL seems to be encouraging it. Am I overreacting?

My sister-in-law (SIL), my husband’s half-sister, has been bringing her friend Chloe over to use our pool, but Chloe has been acting inappropriately toward my husband. She used to wear a one-piece but now shows up in a bikini and never actually swims. Instead, she spends her time chatting with my husband, giggling, and getting touchy by putting her hands on his chest and arms. My husband keeps his distance, but I still feel uncomfortable. My SIL seems to encourage this behavior and has recently made insensitive comments about pregnancy weight and men cheating on pregnant wives. Although my husband hasn’t shown any inappropriate behavior, I’m worried my pregnancy hormones might be making me overly sensitive. SIL wants to come over again, but I want to say no without causing drama. Should I discuss Chloe’s behavior with my husband, or am I overreacting and imagining something that isn’t there?

I suspect my sister-in-law's best friend is flirting with my husband, and my SIL seems to be encouraging it. Am I overreacting?
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