The Pischei Teshuva (E.H. 119:6) quotes the Nodeh B'yehuda (E.H. kama 2) who is mechadesh based on a Rosh (the rosh says that shlucho shel adam k'moso doesn't apply when it is a chov for others) that even though the inability to divorce a woman against her will is a cherem of Rabbeinu Gershom, not m'dina d'gemara. Even the gemara will agree that there is an issur to divorce a woman against her will using a shliach, because a shliach cannot be appointed to do something that is a detriment to someone else. The P.T. there, and the Maharatz Chiyus point out that this is against our gemara in Gitiin 10a that states explicitly that a get can be sent through a shliach l'holacha against her will. The Nodeh B'yehuda pushes off the gemara by saying that it must be referring to a case where the get is actually beneficial to the woman and not a chov. The son of the Nodeh B'yehuda in Teshuvas Shivas Tziyon (88,89) upholds his father's position and writes that he is doubtful that anyone of the gedolei hador that would see his father's teshuva would go against it. Nonetheless, the sefer Get Mekushar writes that the Nodeh B'yehuda is certainly against the pashtus of the sugya and concludes that one may appoint a shliach to divorce a woman against her will.