It's all just language, and honestly she may not know she's bisexual. I didn't, not for a long time. I convinced myself for YEARS that being attracted to women was just because society made it such a big deal. Of COURSE I think that girl looks good, they take the picture to make her look sexy! So yeah of course that's what I think! Even in the queer community there are people that are down on bisexuals, so coming out can be hard. A lot of women especially will use the term bi-curious because they just aren't sure.
Given time I've learned I'm not bisexual. It makes it seem like I am attracted equally to men and women. I consider myself pansexual, since it's been men, women, trans, in betweens! If OP and his wife are at the beginning of this journey, semantics are going to be off and honestly, they aren't even sure yet of sexuality or orientation or relationship model, so I say, cut some slack with semantics.
Me: Late 30s pansexual poly.
DH: My husband of 19 yrs and father of 3 teen girls.
DC: LDR of +4 year