Night feeding

My 6 week old has recently started sleeping longer at night. How long is it ok to let her sleep without eating? I’m used to her waking up every 3-4 hours to eat but we are at 6 hours and she still hasn’t woken up. I was unable to directly breastfed, however she eats expressed breast milk only. (I made hubby give her a small bottle while I pumped tonight and he didn’t agree with me and wanted to let her sleep). She’s healthy, no blood sugar issues that I’m aware of. Full term. Thanks!!