Best friend advice?

Please! Any ideas on what I should do here? My best friend of 16 years suddenly ghosted me, as well as our mutual friends. She hasn’t talked to any of us for 3 weeks, I’ve personally tried messaging and calling her multiple times offering support and just wanting some kind of contact to make sure she’s alive. I thought maybe she got covid and was one of the people in the hospital. Thankfully she’s been on social media, but she’s not talking to any of us and it’s honestly driving me crazy. I’m so worried. I’ve been giving her space and trying not to seem worried but we went from talking everyday to absolutely nothing. Only thing I can think of is I’ve been in school/started a new career and have been super busy more than usual… she’s been partying and doing her own thing which isn’t so much my thing but we’ve always made time to hangout. I’m just so confused and basically begging for advice at this point. Literally we were talking like we always do just fine; and then nothing.