Do you want to keep a log book of her feeding times? Maybe there is a pattern there? My baby feeds irregularly too but overtime I realize there's a regularity in the irregularity... haha. In the morning, he's very awake and likes to play so he feed for a while, play and then feed. The interval is shorter. In the afternoon, he's very sleepy so he slept longer hours, stretching up to 3hours. The interval between feed is longer. At night, he's fussy so he demands more feeds for comfort and for satisfying his hunger. I didn't measure how much he takes at each feed coz he's on direct latching too. But my parents who fed him EBM while they help me take care of him told me his intake also differs along the day. Sometimes he take more, sometimes he take less. I ask caregivers to give 100 or 80ml per feed and then feed him more if he ask for it.
If baby is not with me, every time breast feels engorged, I will pump. Wait until it feels engorged then pump, you won't get oversupply prob again I guess. I had oversupply prob too but I read that over time, it will subside. Oversupply happens when our body still have not adjusted to baby's needs. At this point, I dont't think, we'll get oversupply again. Supply will only decrease gradually if the frequency of direct latching reduces because pumps are not as efficient as baby at extracting milk.