4 Months Old Baby Rejects Breastmilk

Hi Mommies, I have been giving full breastmilk (mixture of refrigerated / fresh -- once expressed out) to my 4 months old baby since birth and I have started giving her thawed frozen breastmilk when she turned 3.5 months old in order to prep her to accept it once I stop expressing breastmilk. But my baby couldn't accept it even with the smallest ratio of thawed frozen breastmilk mixed into refrigerated breastmilk as you know thawed breastmilk tends to have an unpleasant smell/taste. I gave up after trying for a week and return to giving her fresh breastmilk (room temp, once expressed out, non-refrigerated) because we are concerned that she loses weight. After one day of giving her full fresh breastmilk, I realised she couldn't accept refrigerated breastmilk anymore and I feel very worried about this. Any mommies out here experienced the same situation and any advice? 🙏🏻