Please help! Transitioning to formula possibly keeping up milk supply 7 month old.

My 7-month-old is mostly breastfed, with 3-6 bottles of expressed milk weekly while I’m at work. It’s been a tough journey (screaming at the boob, possible CMPA, fast letdown). Lately, she’s been getting frustrated with slower letdown and often stops eating after a couple of minutes.

I worked with a lactation consultant, but even when there’s milk, she sometimes refuses, and she only takes 0-2 ounces from a bottle during those times. She’s dropped some percentiles, so I think it’s time to introduce formula. I also have 45+ ounces of frozen milk but worry about my supply dropping.

I think my ideal situation would be to feed formula during the day so I can start pumping at work and not be concerned about her screaming while nursing and still breast-feed for morning and evening feeding. Any idea if this is achievable and how to get there?

I appreciate any help !!