Baby frustrated with slower flow

ebalkits

So, my daughter just turned 4 months and has been nursing like a champ until the last 2 weeks.  I've had issues with oversupply and just started to finally regulate.  She eats well in the morning, but my 3pm and 5pm feedings have been a nightmare.  She will latch on for 2-3 minutes and then becomes extremely fussy and sometimes so worked up, she refuses to nurse.  At these times, I have noticed that my breasts feel more soft, which I understand is what is suppose to happen when you regulate.  Yesterday, she was extremely upset while nursing that it took forever to calm her down.  I was able to pump an ounce from this breast after several attempts of latching her on, so I know there was at least some milk in there.  I gave her prune juice because I thought she might be constipated and she sucked that down with no problem.  She was rooting after the prune juice, so I offered the breast again and she wanted no part of it.  I tried the other breast and she wanted no part of that one either.  This happened the other day too and when I gave her 5 ounces of expressed milk in a bottle she happily chugged it down without incident.  So my theory is she now upset with the slower flow of milk she is getting in the afternoon as she has no problems while my breasts are full in the morning.  Anybody else have any experience with this?  Suggestions?  I'm worried that my supply is going to decrease and/or she is going to lose weight since she is barely eating during these feedings.  Thanks!