Poly relationships don't come in one shape, so you'll have to talk with her a lot to know how she lives her polyamory.
Asking questions about yourself and where it puts you is legitimate.
The questions I would ask if I were you are:
- is there some kind of ranking between us, am I secondary? Can I expect the same from our relationship as I would otherwise, or will I always come after her when decisions need to be made?"
- are you planning or expecting to have other partners?"
- are you fluid bonded, does she have other partners, do we need to use protection if and when we do start having sex?
- am I expected to have other partners, too? If I like someone, what would you expect me to do, tell you about it before doing anything, or can I start dating them and tell you about it after the fact? If I don't want other partners, are you going to push me to get some anyways?
- without going too fast, is there a future to our relationship, or should I expect it to be short term or not committed? Are things such as living together and having children excluded, or would they be an option if our relationship works? What about getting married (to either of us, as both would impact our relationship)?
- will we ever have dates with the three of us, or will our relationships be mostly "segregated", with you being only with one of us at a time?
- do I get to meet her? When? What's expected of me towards her? How does she feel about me? How does she feel about your polyamory? Is she poly or mono?
About primary/secondary, I suggest you look at other threads for descriptions of what makes a relationship one or the other. Things such as living together, raising children together, sharing finances, making long-term projects, taking (most) vacations together, making big purchases together are all things that usually mean the relationship is primary (they don't need to all be present).