My heart is breaking... I thought Christians are suppose to love "unconditionally"

[drfuzzy]

There are very few xtians who will partner with an atheist.  The xtian belief system teaches that atheists will burn in hell for all eternity.  If your GF believes that, then she would constantly have to try to bring you back into the xtian fold, to save you from her god's eternal judgment for not believing he exists.  If she rejects you for your lack of belief, then it's not going to work.

My personal experience of xtian "unconditional love" is that it only applies to xtians who believe exactly the same things they do.  Everybody else on the planet can burn.

What you have written is completely untrue.

Christians do not universally believe that atheists will burn in hell for all eternity. Sure, some do, but the two largest groups of Christianity (Catholicism and Orthodoxy) do not teach this, and they combine to form the overwhelming majority.

Yes, xtians are taught to love, but just because they try to love you (and not just one another) it does not mean that they will be willing to marry a non-believer because they hold that the two become one flesh and the scriptures are clear that they should not marry someone to whom they unequally yoked in terms of faith.

It's certainly not untrue in my experience.  I work for a Catholic Church.  They clearly and regularly teach that non-Catholics (that means Protestants as well) will go to hell.  Yes, I know many members of more mainstream churches that don't believe hell exists.  These are the ones that will also tell me that they believe the Bible is mostly allegory.  It is heartening to see those numbers grow.  They still look at me like I have lost my freaking mind if I tell them than I'm an atheist though.