Looking to date? Or dating? Is she interested in dating you?
I would say that until you're in a relationship you can't really even broach the subject. Acting jealous before you even start dating may turn her off. It would me.
If you are dating, then ask her if there's ever been anything between them or if there still is? If she is an honest person she'll be transparent about her history. Even if they have a history doesn't mean that there's anything between them. How many times have you kissed someone you thought you liked only to find out that there was no chemistry? And just because there was chemistry before, doesn't mean there's chemistry now.
Whatever she tells you, just take it at her word, and find a way to move past it. Unless it's serious, asking/wanting her to change her living situation is asking a lot from her.
Men and women can coexist without it being sexual or romantic, regardless of sexual orientation. Roommates don't always spend time together either, it's sometimes a situation of convenience.