Get down there bang on her door & invite her out for a walk. Tell her you’re in love with her dog & can’t get Fido out of your mind. If she’s hot get her banged before you’re listening to her giggling in the hallway with her alpha trying to find her keys. Work it out from there & stop procrastinating on what might have been. If it goes horribly wrong after you’ve banged her, things usually work themselves out. Friend zone her, spin her as a plate & don’t commit to anything. Doing nothing is worse than trying & failing. If she sees you as a guy with no options she’s going to ignore you. The accidental meeting will only work a few times before she’s onto it. Off course you’re going to bump into each other sometimes. If your not comfortable with the face to face approach Get her number, or give her yours by telling her it’s incase of emergencies & her dog is ill or the apartment is flooding. Make something up..! Once the number is in your phone, a few messages may heat things up..! Go for it before some other neighbour does what you wished you had done.. good luck..!