The Gemara says that those who can withstand an insult and not insult back bring Geulah to the world. However, that probably does not apply in such a case where by not showing the other girls that they are hurting you they will continue to be Over on many Aveiros D’Oraisa (Lashon Harah, Ona’as D’varim, and more). If I were in your shoes, I would respond that while your brother may currently be OTD in Bein Adam LaMakom, they are just as OTD in Bein Adam L’Chaveiro.
