You're totally fine to feel what you're feeling. Sounds like you were a little blindsided, even though it probably wasn't deliberate, or if it was, maybe it was out of a sense of protecting your feelings, your relationship or perhaps that she really didn't see whomever she was talking to as anything more than a masturbatory aid and so didn't bother to disclose since it's not going anywhere on an interpersonal level. But fair enough that you'd like some of her sexual attention, too, unless you had a previous agreement that sex was not part of your relationship. If it is, then have you (either or both) been taking it for granted? And therefore it's lost some spark?
Thing is, so much is often unspoken in a relationship. Like, we play by societal rules that we've kind of absorbed over the years and accepted without really questioning them. But then we perhaps question some of those and even open the relationship up beyond absolute monogamy, but we don't actually know all the possible things that could trip us up as we figure it out. Sure, there are some great books out there with discussion checklists and so on, if you like that kind of thing. But the more likely scenario is that you'll have to deal with things as they crop up, and this is usually best done through effective communication. Rather sounds like you need to go communicate with your wife. Do you both know how to do this without pushing each other's buttons?