For those who do it, how? Do you pump and mix it? Just give a straight bottle of formula?

My 4 week old has been sitting up/vomitting. She spits up and then immediately wants to eat again so weve been having a hell of a time. She is literally feeding every half hour to hour day and night unless I can get her to take the soother (which isnt often) to prolong it a little. I had some formula left from when I was supplementing til my milk came in so gave her that last night at 2am with her feed. She drank 2oz of formula and fed roughly 10-15 minutes on each side. She slept 4 hours before getting up to eat again, and didnt spit up all over. So I want to supplement a little since it seems to help. Just not sure if I should pump and mix or just give the straight formula like last night? Or does it even make a difference?

This just started like a week ago. She was fine up until then . Eat every 2 -3 hours during the day, and then 4ish hours at night except when she was cluster feeding. My midwife doesn't seem concerned and said if its reflux they dont do anything about it anymore unless shes losing weight or dehydrated. So I'm just trying to do my best to make her feel comfortable. Shes so miserable like 70% of the time when shes awake now.