¿De qué manera podría animar a mi amiga a la que acaban de dejar?
Siento que a tu amiga la hayan dejado hace poco.  Yo le preguntaría si quiere hablar de ello o distraerse.  Si quieren hablar de ello, buscaría un lugar tranquilo y una bebida caliente y escucharía.  Si quieren distraerse, buscaría un bar o una actividad favorita que le guste a tu amiga y la llevaría allí.  Llama al mayor número posible de amigos comunes y proporciónale un amplio abanico de distracciones.
What are some ways I could cheer up my friend that just got dumped?
Im sorry your friend recently got dumped.  I would ask them if they want to talk about it, or be distracted from it.  If they want to talk about it, I would find a quiet place and a warm beverage and listen.  If they want to be distracted from it, I would find a local favorite bar or activity that your friend enjoys, and take them there.  Call as many of your joint friends as possible, and provide ample supply of distractions for your friend.