I sort of think a hotel would be a good location. Have a small party in a hotel room.
A number of scenarios can take place with less risk than outside or in the street:
1. Have her locked out of the room with a bath towel around her. She can bang on the room door, but don't let her in. Have the other girls out in the hall enjoying her struggle (maybe one with a video camera). They can take her towel from her when an audience grows, and run down the hall with it.
2. A hotel with two or more floors might be fun, because the two girls can cast her into the elevator with nothing on. Be sure to have them push all the floor buttons before the doors close. It might be good to have a camera waiting down in the lobby, along with everyone else waiting to ride up in the elevator.
3. Light bondage is always fun. Tie her nude to a chair or bed, and have the other girls take pictures. Maybe then invite a few surprise guests after she becomes a bit comfotable with the crowd that's already assembled.
4. Have the girls take polaroids of her in the shower, and then threaten to share them with others. See if she'll follow them out the room door and into the hallway to retrieve the photos before the other girls slide them under other random guest's doors.
If she does follow them, you can race the other two girls back to your room, and close the door... easily transitioning to idea #1 (with or without a towel).
5. Order room service, have her answer the door in a towel or robe. Have the other two girls run over and pull it off while she's handling the transaction with the server.
Of course, with any of these scenarios... you need a camera (or multiple cameras!)