Hey lovely! I'm sorry your little one is sick and it's clear you are a wonderful mama to think about giving your baby the best milk you can when they are sick. The antibodies in breast milk are so beneficial to help babies when they are unwell and even to help them prevent getting sick. Any amount of breast milk is beneficial to a babies immune system and it's amazing you have colostrum to defrost - this is a powerhouse of virus-busting antibodies and nutrients. Breasts can still produce milk weeks or months after stopping and re-lactation is possible with regular skin to skin,latching and pumping every 2 to three hours. Sleep power pumping is great for this. Can you contact an lblc lactation consultant in your area for support? This article explains a bit more; https://www.ynhh.org/articles/can-you-start-breastfeeding-after-stopping
*power pumping not sleep power pumping 😅🙈
You could try it and see what happens if it is something you want to do, but don't put pressure on yourself. She is fed and loved and that's what is important.