We ran through this when my kids (and a couple nieces and nephews and one day care family

) were preschoolers. It sucks, and it can last a long time. A couple different doctors involved in all these cases and since we were all dealing with it, the parents shared what each doctor said. The VAST majority said to leave it alone and let it pass. Only two treated (one with freezing and one with a blister beetle solution.
My only advice: don't use the "blister beetle" solution. I don't remember the exact name, but it comes from a beetle and causes the molluscum to blister over and slough off after a couple days. But, it will cause permanent pock marks on their skin. I used it for my son because the combination of molluscum and his eczema was becoming a major issue. It worked, but it was painful, took several treatments (because new spots would pop up and we would have to treat those), and did leave permanent marks (we were warned it would). I don't think your daughter would be happy with those scars. The molluscum eventually went away on every other child who just left it alone and there are no scars.
One other word of warning. My daughter had it under one arm (pretty mild compared to our son) and it went away, then actually recurred about a year later for a short time, and hasn't been back since. Seems like most cases only happen once. I'm guessing hers came back only because the first case was so mild, but wanted to warn you it wasn't impossible.
I feel for your daughter, 13 is a terrible time to be dealing with this. I have heard the over-the-counter tea tree stuff recommened (on the Dis) before and it seems to be fairly successful. Might be worth a shot.