Did you reply to her text about not being given enough time? I think that response deserves a well thought out response to let her know that as per your contract it states that you give parents ASAP notice of the daycare closing and you did just that. You need to address that it is up to her to find other care if you the daycare is closed. I try to keep my written communication between daycare families and myself business and keep personal out. If you did reply to her text, I think a follow up memo so there are no further misunderstandings.
I'm guessing that it's probably stress related as maybe she had something big going on a work but - there is NO reason for her to say that and make you feel bad THEN expect you to find a replacement. She forgot to put her sensitivity chip in when getting ready for the day!!
I hope your son is feeling better and don't let her stress you out when you already have your hands full with your little one