The previous owner told us that there's a really sweet cat in the neighborhood that goes around all the houses, named Madison. I hadn't seen any evidence of the kitty until last night.
I walked into the kitchen and saw Gretchen at the slider door, and she was not making happy noises. Turned on the outside light, and there was Madison! Lots of hissing (mostly on Gretchen's side) and some scratching at the door (Madison's side). Lots of growling.
Suffice it to say, I do not think they will be besties and I think my friend was right when she said Gretchen does NOT like other cats! (my friend/coworker volunteers at Animal Control and was there when Gretchen was on her two week hold before we adopted her)