Am I wrong to be annoyed/a little upset?

Tonight I am leaving my baby for the first time to go out with my husband for a couple of hours. We asked his little (22 year old) sister to babysit (asked her back in February when I planned this date). This afternoon she texted me and asked if she could bring her friend along. I've never met this friend, only seen instagrams of them partying together. I honestly was irritated that she even asked, but I said sure. I didn't feel like I could say no, that's just me. I'm just wondering how others would feel in this situation. I'm just a very attached mama and I really don't like leaving my baby so it's hard in the first place, and now I'm having a girl I've never even met around him in my home tonight. I won't be asking my sister in law to sit again.

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