Would this piss anyone else off?

My husband and my MIL were on the phone last night, and my MIL told my husband that she was going to come visit us on Tuesday for the whole day, and I could just "go to the store or something."
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Like she is making plans to send me away so she can have alone time with my 2 month old child. 
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I told my husband, no she isn't, so he told her that she could visit that evening when he got home from work. 
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Was I overreacting, or would you be mad too? She always says she just wants to give me a break, but I'm not asking for a break! And let's be real here, she's not really trying  to help, she's just trying to get my baby all to herself! He's only 2 months old, I'm not comfortable leaving him alone with her or anyone but his dad yet. I wish she would just back the F off!