That sounds very stressful Dido
I think you really need real-life help with this - have you called the ABA for advice? Have you seen a lactation consultant?

DS went through a period of breast refusal and a slightly younger age. It started for us as he suddenly switched to having much shorter feeds and I thought he wasn't getting enough, so tried forcing him to have more. The way to beat refusal is to be patient and relax (which seems impossible when you're worrying about your child not getting enough, I know).

Try to relax at feed times and don't ever push it.
Try feeding somewhere different - a quiet darkened room might help. Or feed in the bath.
Try feeding when she first wakes up from naps - sometimes they're more amenable when they're still sleepy.

It seems she is feeding well overnight - perhaps she's too busy during the day to feed. It's not unusual for that to happen to some extent. When having solids she can still sit up and look around, but at the breast she can't see what's going on. During the night it's dark and quiet anyway, so she figures there's nothing better to do...

On supply - it wont' disappear so quickly, your breasts are just adjusting the change in feeding patterns. They'll make milk when she wants to feed
Hopefully it will be a short phase - all the best~~