Am I being pregzilla?

This is long, sorry but I really need some advice. I have this coworker. I hated her before I got pregnant but now she's driving me so nuts I'm having dreams that replay the workday I just had with her. She's 20, and in my opinion acts 12. Things that bother me about her, she makes more than a dollar more than I do, but has worked there 2 years longer. She is never on time and as soon as she gets to work she eats, poops or plays game boy. She will interrupt me when I'm talking to a customer and completely take over the conversation. She doesn't actually ever stock anything. She isn't professional when working with customers- she will make customers wait in line while she talks on the phone/ treats or baby talks her dog (pet store). She sings and whistles which drives me crazy and when I ask her to stop so I can think she will get in my face and do it louder. Call "dibs" on doing invoices when there's still things to do on the floor. Tells customers her business and mine (although I've completely stopped talking about my life outside of work to her). Something that happened yesterday (my Monday) was she whined at me for not doing the cat box (I haven't been since I'm pregnant, the boss knows, and I haven't done it for months but she doesn't know in fear she will tell everyone about the pregnancy) my excuse for not doing it was I was too busy for cleaning and finishing putting the order away that came 2 days before (which is true). She also told a customer "everything's a competition between us" when I was peeling tape off the wall that she had hung something up that was crooked and got the tape all bubbly and ugly. All I was doing was redoing it to make it look nicer. There are only us 2 employees and the owner. The owner is passive and clueless. When j went to ask for a raise (shortly before I knew I was pregnant) she changed the subject and pulled a sting ray tooth out of his pocket and showed me. I'm quitting after the baby is born, but that's 6 months away. I really need some help on how to deal with this. Anyone? Please?!