Sweet P (6 weeks now!) is fed exclusively with donated expressed breastmilk, but I'm having a hard time getting reliable answers online because most of the information I'm finding refers to fresh breasmilk instead of frozen.

My main question- If she doesn't finish the full bottle of breastmilk in the first sitting we return it to the fridge and re-use it for one more feed (warming it in the breastmilk safe Kiinde Kozii bottle warmer). Do you do the same?

I feel like I learned that this was safe 2.5 years ago when we brought home Little P and he was fed the same way, but now I'm having a hard time finding where I got this information and I'm afraid we should be throwing out the milk if she doesn't finish it on the first feed (which would be devastating because I hate throwing away unused liquid gold!).