mandymac, I'm an expert in keeping babies awake to feed - ds was a terror and would fall asleep after only 2 sucks. How is your dd's weight gain? Ds was very slow, so I had to work really hard to get him to feed for longer, but if your dd is putting on enough weight it could be she is really efficient.
Things I found worked were...
blowing on cheek, tickling feet etc to start with.
THEN, undressed ds, put him back on, THEN lay him down on cold changing mat (feels really really cruel), put him back on, THEN throw cold water on his face (just a few drops, you don't want to drown her!). If you keep switching sides, then there is a more ready supply of milk to keep her interested and awake, rather than having to work harder for the later milk. This goes against the advice to keep them on one side per feed, but if she's falling asleep before she reaches the hindmilk anyway, then it will be beneficial - it's mentioned in the La Leche League book 'The Womanly Art of Breastfeeding' (!) as 'switch feeding' and says you should switch to give at least 2 goes on each side (this is only for a sleepy feeder, not general advice).
You can also express a bit of milk to top up at the end of a feed, but tbh I found it a real pain having to sterilise everything all the time to extract the 1/2 oz of milk that didn't really make a lot of difference!
I would have thought 45 mins to an hour would be plenty - they're only supposed to go 3 hours anyway (which is beginning of feed to beginning of feed) and they do need some sleep/kicking around time! The key thing is that she is actually feeding, not 'nibbling' - you should probably be able to hear her swallowing.
Hopefully tiktok or mears will see this and give you some qualified advice! Congratulations on the baby btw!