Freezer Milk ?

I have been EPing for 9 months {gives self pat on the back}. I am only pumping twice daily now. I get enough for two bottles a day and she gets two bottles of freezer milk per day.  I guess I'm a little baffled on how to properly thaw and use my freezer milk? My little lady takes around 5-6 oz at each feeding. If my freezer bag has 7-8 oz in it is it okay to use it in the next bottle if its been thawed in warm water? When I started freezing my milk I made the silly assumption that she would be drinking giant bottles in the future, and that's just not the case! Can you lovely ladies tell me your thawing/use process? Thank you!