What would you do about someone leaving furniture in your apt. for a long period of time? (see details)

Okay, so I moved into an apartment about 3–4 months ago with a girl that had already been living here for a year with someone else. The girl that previously lived here left two of her couches and said she would take them as soon as she could find room for them in her new apartment. It has been over 3 months now and she still has not removed them. She has told us countless times she was going to come and get them on a certain day, and then she never shows up. My roommate and I are getting really frustrated, and we have told her repeatedly she needs to come and get the rest of her things. We even would be willing to get rid of them for her, and or if she no longer wants them, sell them so we can get a new couch. How would you go about solving this issue? I’m starting to think she is never going to come back for them. I don’t want to get rid of them though and then have her come back and say she wants them. Help! Thanks =]