Going back to work.. advice!

Courtney
So for the past month in a half baby has consistently woke up around 5 in the morning, I fed her, and she would be back asleep by 6 at the latest. That worked great! It would give me plenty of time to get ready for work. BUT these past two days.. she has slept all through the night, waking up at about 8. So now I don't know what to do for tomorrow (my first day back).. do I set an alarm and wake her up at 5 to feed? Or do I just let her sleep and pray she doesn't wake up in the middle of me getting ready and making me late for work? 
I don't have to drop her off at daycare or anything, my grandma shows up at 6:30 to watch her. So if she wakes up then, it's fine. But I'm worried that she will wake before then and I won't be able to get ready.. I just don't know if I trust the schedule she's been on for two days or try and go with the one she had for a month in a half.