May Allah guide her back to The Truth, Aameen.
I feel like crying when I hear stuff like this, poor girl, I feel sorry for her.
A Pakistani boy in my town use to say he wasn't Muslim just to suck up to his Non-Muslim friends and then he died suddenly in a car crash, they didn't offer his Janaazah or bury him in the Muslim cemetry.
The grief his parents went through and still go through everyday, atleast had he died a Believer they would have been content that he's gone to Jannah and beable to get over him dieing after a few months.
That incident gave me goosebumps, religion is not a joke or a fashion accessory, at least if we die Muslims (even sinful ones) we will one day attain salvation from Hell on account of our Faith, even if its an atoms weight worth.
Oh Allah whoever amongst us you keep alive let us live upon Islam, and whoever amongst us you cause to die let us die with Faith, Aameen.
Prophet Jesus (peace be upon him) himself preached Islam (Submission to God Alone, rather than the Trinity) and he prophesised the arrival of Prophet Muhammed (peace be upon him) so it's silly of her to abandon Islam. We already have Christ/Messiah in Islam and when he returns to earth, it's the Muslims he will be with, for he, his mother (pbuh) and his righteous disciples all followed the message of Islam
I met a Jew once who said even they believe that Prophet Moses (peace be upon him) prophesised the coming of a Prophet who is most likely to be Prophet Muhammed (peace be upon him) but he said they love Prophet Moses (peace be upon him) too much to leave him for Prophet Muhammed (peace be upon him), I told him you wont be leaving him at all because belief in him is an integral part of Islam.
Let us Pray for her and all other misguided ones, may Allah(arabic)/Elohim(hebrew)/Alaha(aramaic) save us all from misguidance and guide the misguided through His Grave and Mercy, Aameen.