Cat on the porch

Today, I was going to sleep in as late as I wanted to, catch up on everyone's blogs, get up, go christmas shopping while my hubby and father in law did electricity in my house.
Didn't really work out that way...
the outside cat, who is not ours, but that we feed and let sleep on our porch in the winter hobbled up the driveway today with a gash in her right side.  Hubby was upset (he's the bleeding heart) and wanted to know what we should do.  I came in looked up the name and address of the emergency vet and took her in.  A whole lot of money later, the cat is groggily waking up on my porch and despising the cone around her head.  I can't let her inside because she has fleas and my cats don't have their shots.  So we are trying to figure out a way to make her comfortable with lots of blankets and the storm windows in on the porch.  Not ideal, but better than her being out in the wilds with an open sore.
I thought I knew who she belonged to, so I went and left a note today.  The woman just called me and told me that it wasn't her cat.  The cat now needs to go to the vet and have the drainage removed and the stitches out.  I don't know what to do...I honestly can't let this cat in my house and I don't think that the shelter will take her with this kind of injury.  I wish we could keep her but we really can't....
So that's put a bit of a sad note on my day...I can't figure out what to do with the cat....but my father in law is here and he and my hubby are working on the electricity as we speak....so that's good...means we will be able to plug in the treadmill and the freezer...very exciting stuff happening in my house...beyond that it means that all of the uninsulated, fire-waiting-to-happen wiring in the bottom half of the living room has been replaced with insulated wiring that is up to current codes...this is something that makes me smile...