"'Everyone who divorces his wife'" (Mt 5:32) is today considered the guilty party. She is the innocent party. He "'makes her commit adultery'" (:32). Adultery is voluntary sexual intercourse between a married man and someone other than his wife. The assumption for this to happen is that she remarries. Since adultery is a sin then remarrying under unscriptural circumstances is sinful. Legalistic interpretation is that you cannot remarry unless the exception clause applies. Divorce would be acceptable for "'the reason of unchastity'" (:32). Legalistic exegesis would support that the adultery which occurs is due to the sexual relations in the new marriage while the previous marriage was still in effect.
Since the definition of adultery is illicit sexual relations then there must be an act of it. The Pharisees knew this for they tested Jesus by presenting a "woman caught in adultery" (Jn 8:3). The woman was apprehended "in the very act" (:4). But if the divorced woman never remarries then the sexual part is missing unless you assume she does remarry. However, once you start reading assumptions into the context then when do you stop?
The definition of "adultery" has another aspect. Jewish society enacted regulations to protect people like any other society. The husband had an exclusive right to his wife to ensure that children born to her were his own. Trespassing this would be categorized as such relative to his protection being violated. Could Jesus be labeling it in terms of its larger concern as opposed to its obvious sexual meaning?