Transitioning to formula milk

Hi mummies! I've finally made it pass the 1 year breastfeeding mark 🎉🎉 I'm planning to transition to formula milk as supply is getting low BUT baby is refusing to take formula milk at ALL! We tried to feed her in her sleep but she noticed the difference and woke up right away. #advicepls Can we mix the breast milk & formula in the same bottle and slowly transition?? Thanks in advance!