Letter writer ghosted me.

my science professor letter writer ghosted me. i literally asked her back in October and met with her and she said she’d be happy to write a letter. i tried emailing her 3 weeks ago and got no response. i followed up last week and got no response. i don’t know what to do. i don’t have connections with any of my professors. do i start desperately emailing every science professor i have to see if someone will reply?