Aside from everyone's advice to keep Mushroom indoors, 4 Feline's has the best advice about getting Mushroom in before dark.
I used to have the exact same problem with my black cat, Magic (rainbow bridge). If I went to pick him up at say 5 - 5:30 I had no problem. But if I waited any longer he was already "in the mood" for dark and adventures.

I too, hate to confine my cats to the house, but with ferals running around loose, I just don't have much choice. It upsets me to see them hurt. And Spencer is so right about the possibility of diseases.

Lots of toys, catnip, scratching post - good play time from you - could keep her happy and safe. And usually there is so much traffic around apartments and people drive way too fast - too fast for a kitty.

Good luck with Mushroom - what a great name.
And isn't she clever to use that board and get in and out of your apartment. Sounds like she sent open invitations to her neighborhood buddies - free food at my house!!