Frozen breastmilk, what do I do with them?

I have 2 boxes of frozen breastmilk left. I’m wondering, what I should do with them? My 9mth old LO doesn’t like the taste of frozen breastmilk. Tried to mix into her oats but it gave her bad rashes on her cheeks and chin when she got some of the food on her face. PD says it’s infant dermatitis as her skin is sensitive so after feeding wash her face and chin and apply Ceradan cream which I’ve been doing religiously. I stopped mixing the breastmilk in her oats so the rashes are not that bad anymore. Wondering what I can do with the leftover milk? Can I mix half of it with her prepared formula milk to hide the taste? I.e. 60ml breastmilk and 60ml prepared formula milk and give her the 120ml? ?