Backgammon, I remember your story from the other day. It's great you are now back home with her.
It will help, I think, to call one of the bf helplines and talk to someone about this. A good breastfeeding counsellor will listen to your story, and will understand your feelings and the way your confidence has been knocked. In addition, she will help you work out a plan to get back to full bf. You are doing the right thing at present - using your own milk when you can as a top up - so that's a good start.
However, feeding for 45 mins and still accepting 60 mls can be part of normal newborn behaviour. Babies love to suck, and need to do so - many newborns just want to be close to mum, on and off the breast a lot of the time, with the option of sucking for much of that time, too
What happens at 45 mins? Would your dd remain on the breast, perhaps if you swapped sides? Would she go back on after a little break? Is there a reason you stop bf her and give her the top up then? If she is feeding effectively, and has the energy and will to feed (that is, doesn't drop off to sleep all the time after a short burst of sucking because she's too tired to do much more), then keeping her on the breast is ok - there is no magic about 45 mins
If there is still an issue about weight and feeding effectiveness, then topping up may still be necessary for the moment.
Do call one of the lines, and keep posting here, too. I hope we can help you gain your confidence again