Not Hungry For 8 Hours

My LO is 3.5months old and she can sleep for 8hours straight without any milk. We tried to wake her up in between (4hours) for feeds but she drank around 30ml and will fall back asleep. After 8 hours, she finally wakes up - still no signs of hunger (we tried feeding and she also reject). What surprised us is that she continues to smile and blabbers baby language to us, looking satisfied and contented. Her diaper change is about 6 to 8 times, normal to her diaper change when she was 2 months old. Any mom also face the same issue? (the only time she could finish her milk is when we dream feed her in the middle of the night). Weight gain wise, about 150g per week. I am EP mom btw. Is she rejecting my milk?