To answer the op..please don't talk yourself out of a night out. You have, like you said, put dd to bed every night of her life since she was born..so you deffo deserve a little break and me time. I was supposed to get out last night and didn't because my mum got snowed in and I qa devastated as I don't get out much. If you have the opportunity do it!
I suppose though it depends on your child and the person looking after them. For example me and my mum sound exactly the same (my own dad can't tell us apart when were on the phone) so she can seem to soothe ds slightly better...obviously my ds is aware its not me but I know he is alot calmer with her than my mil and he sees them both an equal amount of time.
Now, a few weeks ago, my inlaws came up for a night and persuaded me to go for one drink at the pub around the corner and let my sil who's 16 listen to the monitor (I had put ds to bed myself) and I refused at first because I told them she wouldn't be able to settle him at all. Anyway, long story short I went after giving her strict instructions to call me of she could get him back to sleep..and when I came home an hour later I could hear him crying when I got in..she didn't get a chance to get her mobile. It was only five mins though and I was only around the corner so a bitd different I suppose.
Anyway..it's true that babies have no conception of time when they're little...you leave for a minute or an hour and they still think its a lifetime and that you're not coming back. They ARE primatively connected to your scent and will notice you are no longer there..and they can also recognise your heartbeat so notice this if being soothed by someone else even if they smell of you.
What I will also say though is that at 10m your dd is very perseptive and will start to learn cause and effect..my ds went through bad separation anxiety so I read an article which advised to play peekaboo on a daily baisis using muslins and get baby to do it to themselves and pull it off your face ect. And also to be clear when you're leaving that you're leaving by making a big deal of saying bye and teaching them to wave back. After I did this leaving him with the Childminder was a lot easier.
Just relax and I'm sure she will have a ball with nan..shell probably tire her right out and shell collapse in a little cute heap. Plus, she already has built up a relationship with your mum during the day so it won't pit her nose completely out of joint iykwim.
I hope that helps and I really, sincerely, hope you go and have a smashing time

x
Previously Princess87