Okay so I have a bunch of frozen breastmilk still from when I was pumping and I just haven't been giving it to her…

Okay so I have a bunch of frozen breastmilk still from when I was pumping and I just haven't been giving it to her because I don't really know why. I guess cuz I'm sad that breastfeeding didn't work for us and that reminds me... anyway, I decided today that I need to start giving her some even if it's just one bottle a day because a. Some breastmilk is better than none and b. We have so much in the freezer. Anyway, I gave her a breastmilk bottle tonight and within seconds of her being done, she projectile vomited it everywhere (we're talking baby needed a bath, I needed a shower and we had to change the sheets on our bed😭) so anyway, now I'm at a loss for what to do. Is the transition maybe just too hard on her belly? She's only projectile vomited like that two other times and one of those times was when we tried to give her the ready made formula that we brought home from the hospital a few weeks after she had already been on the powder... so I'm assuming that her belly really just can't take the transition. But what can I do with all of my milk?😭😭 I was thinking about maybe adding an ounce to her formula bottles to make it easier on her tummy.. but I just need some advice. I'm going to talk to her pediatrician about it but her next appt isn't until sept. 8th and it just doesn't seem like something I need to call over.