As this is something I struggle with personally: She may be someone who doesn't easily say 'I love you'. And I think it is strange to expect the other person to answer instantly in the same fashion just because he said it first ... what kind of pressure! I wouldn't feel comfortable at all with this. (If it is because of her bf .. I would question her poly-ness in general, what does the bf have to do with this? Is she cheating on him?)
Facts: 30, female, bi, v-type relationship with Sward (husband, straight, mono) and Lin (boyfriend, straight, mono), poly-fi and co-primary.