Update:
almost everything has cleared up as the week's gone on! she still has the bigger blister, but the two smaller red ones went away, and the black stuff has gone away too
I think that wiping her like a baby after she's gone potty really helped, she just wasn't cleaning herself properly just needs a little extra help!
the bigger blister hasn't gotten bigger or smaller, so still watching that. the black pores/residue... I think that may have very well been yeast.
as far as canine herpes, i don't think so, those are small clusters, this is just one normal blister. :/