Well there ya go. Sounds like it worked out great, and you did the right thing by showing her some basic decency and giving her the chance to work it out.
It appears I'm all alone in thinking that I can kind of understand how your ousted singer feels. If you guys have never used subs before and never discussed your plans for dealing with this type of situation, and she had a serious, legitimate reason for missing the gig, perhaps she had some basis for being hurt.
Speaking of having a serious reason for missing; I strongly disagree with the person who compared this to a major league football player missing a Monday Night Football game. A better comparison would be that the football player canceled a fishing trip with his buddies to play MNF. She said she missed for work: If we're going to talk about this as a job, we have to talk about "primary" job and "secondary" job. For most of us, playing music is a secondary job, i.e. it does not pay our living expenses. Therefore if a serious conflict between this secondary "hobby job" and our bread and butter job arises, we are smart to place our primary job first. If it came down to canceling a gig or losing my job, I'm canceling the gig. Of course, getting a sub is better but what if the band has never discussed the possibility and someone you care about gets hurt over it?
Not only was it right to give her another chance, if it were me I would've probably been reluctant to use a sub without her approval, depending on lots of possible variables that we don't have... and if she was that hurt I can totally see her not being able to work with you any more.
