Baby drinking less at night

Hi mummies, My baby is around 5 weeks old. I’m exclusively pumping. I feed her every 3-4 hours and she usually drinks 120ml per feed on schedule. At night this 2 days, she drinks only 50ml-80ml and rejects the bottle no matter how hard I try. It seems she just wants to go back to sleep. I tried offering my breast directly but itshe rejected too. One thing I noticed is when I feed on schedule, she can’t seem to finish the bottle. When I feed on demand, she can. But I’m worried feeding on demand is too long a span from her last feed as it usually exceeds 4 hours. Is this normal? I’m just worried she’s drinking too little per day. She doesn’t appear to be irritated, still smiling and active most of the time.