BM/ FM preference

Does baby have milk preference? I think my baby does 🧐 from the way she finishes her milk. My baby is on BM in the day and FM at night, when a 100ml BM is served, it will take her 2/3 times to finish the milk. For example, 10am I feed her BM, she will drink 40-60ml, so I will keep the remaining back to the warmer, and feed again within an hour. The cycle repeats, I don’t see her finish the BM at one go unless she is super duper hungry. But during the night or when we go out, she finishes the FM at one go. Or maybe some little left over. Sometimes she will also drink 40-60ml and I will keep warm the remaining like how I do for BM. Am I overthinking? Isit due to the amount of milk she can intake or maybe really she prefers FM?