Hi, welcome to the board.
I am sorry you can't just enjoy your new relationship, but have to deal with your partner's mourning so soon. Like any grief, it can be overwhelming and all one can think about.
But it sounds like even before their breakup, she spent too much time talking to you about him. You want your time with her to be about you two, not all about her bf. So, that is an underlying problem...
For now, enjoy the break while she's away for xmas. She can probably process her grief with friends and family back home. Likewise when she's back, you do not need to be her only shoulder of support. You say you have mutual friends. Maybe encourage her to talk to them about her bf, and get your ass out of there so you don't need to feel hurt and unspecial, almost invisible. Do this as often as you need to. Otherwise I am afraid you will start to feel used and resentful and bitter.
Actually I feel there's a good chance she will get over him starting his new relationship improperly and they might get back together. Gird your loins for a wild emotional ride. I agree you could start a blog here to express your feelings around this unfortunate event.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
There's no lying in polyamory!
I'm a 58 year old woman with 2 partners:
miss pixi, my live-in gf, 36 (together since Jan '09)
Ginger, bf, 61, married, lives nearby (together since Jan '12)