MIL worries

So me and my husband are going out on Friday with some friends for a triple date for Valentine’s Day. We’ve got a table booked for 6:30-9:30 so we’d be out from 6-10pm. The plan was that my MIL is coming to our house at 5:30 to look after our little girl (5.5 months), feed her and put her to bed (usually around 8:30/9ish) and then just leaving when we get back (I’m not planning on drinking). So I’m a FTM and my anxiety has been quite bad since having my little girl, particularly in relation to SIDS. We’ve been sticking to all the guidance, such as always being in the same room as her when napping/sleeping, and I told my MIL this. Obviously my little girl still sleeps in our room and due to us just moving in before she was born, literally the only things in our room is our bed, my girls next to me and built in wardrobes, no TV (we’re planning on sorting our room out properly when we eventually move our little one into her own room and we have the space - I know you can do this at 6 months but we’re planning to a bit later just because of how worried I am). I spoke with my MIL earlier today about the plans for Friday again and she asked if the baby monitor could be set up as when she’s put her to bed she’s just going to go downstairs to watch TV as we don’t have one in our room. Our baby monitor is obviously still in the box as we have no use for it currently. I said that I’d rather she stay with my little girl until we’re back as we’d spoke about previously but she just said “well you don’t have a chair in your room or a TV and I don’t particularly want to sit on the bed in the dark until you’re home”. It would literally be for an hour but I suggested taking her phone and some headphones up which is what we do if we want to watch something although I usually just go to sleep when my little girl does🤣 She complained a bit more but eventually agreed. Now I’m debating coming back for my girls bed time or just not going at all because I’m absolutely petrified she’s going to just come downstairs and leave her asleep upstairs. This is only the second time I’ve left her with my MIL for a few hours and before it was during the day. Am I being silly for being like this after she’s agreed? I’m just so worried she’ll not do what she’s said and just come downstairs.