How do I go about this without seeming like a bitch?

So about a month ago my best friend and I went out shopping and wound up in petco. She fell in love with a guinea pig and bought it without hesitation. She and her boyfriend live at home with her mom and she didn't call either of them to make sure they were okay with it, turns out they weren't. She was told she couldn't bring it home so she either had to find somewhere for it or take it back. Now the guinea pig lives with me until she and her boyfriend get a place of their own (they're looking for a house to buy now so the anticipated time the guinea pig would be here isn't supposed to be long), and even better, it turns out the guinea pig she bought was pregnant so I now have 3 in my house. I have decided to keep one of the babies (the boy) and it's in its own cage now while she plans on keeping the mom and the other baby. The deal my SO and I made with her when agreeing to keep the guinea pig here was that she would pay for everything and she would have to come clean it's cage when it needs cleaned, I would feed them. Twice now, I've called her and told her the cage needs cleaned and that it was smelling up my room and she has not come to clean it, I told her two days ago that it needed cleaned, reminded her yesterday that my room was really starting to smell, and called her today asking if she was going to come clean it, her response to that phone call... I'm actually going to spend time with my mom, I feel like I haven't gotten to do that the past week. This past weekend she went on a trip to Ohio with just her mom. I just don't know what to say to her to make her aware that this is bothering me without seeming like a bitch. any suggestions?