It'll be just fine!
I was a nervous wreck the day Zoe got spayed as well. I had class that day, I'd hoped it'd keep me distracted. I was so focused on it though it didn't distract me. But in the end, it was all for naught .... Zoe got out of surgery just fine and eventually adjusted just fine. The first night she was just sleepy, the next day she was in pain before she got her meds and then believe it or not by the 2nd day she was 100%!
If Mandie is anything like Zoe the hardest part will be keeping her calm and not hurting herself while she needs to recoup! Zoe just wanted to run around, climb stairs, jump, etc.
Our thoughts will be with you though!