Is it against Christianity to marry an atheist?

The default position is that it shouldn't happen. The Bible talks about being "unequally yoked" and that it is a BAD IDEA, and real life confirms this as Christian/Atheist marriages tend to be full of major problems because of competing worldviews. Having said that, there are instances where a Christian marries an atheist and the atheist ends getting converted and then they live happily ever after. I would say that Christians should marry Christians, but the only exception would be if somebody is close enough to God to actually hear him and God tells that person to marry the non-Christian.

Who cares, as long as her partner is a good, honest, respectful person who loves her.

Unequally yoked isn't the same as unequally poked . 

Paul never got laid , was short bald and probably smelly  so is that what made him an authority ?

 If you Pauline people would drop Paul and ONLY follow Jesus .

 And how do you know some atheist might be able to help you understand Christianity better than some once in a Sunday flop on pew and view . 

Since you are so deep into theology how about Gods' Plan .

 All X&Christians believe in Gods' Plan . Calvinism IS Christianity as much as any Protestant sect . Maybe Gods' Plan is to have the Christian marry a atheist and 

convert the atheist to the Christian Cult . How will you people keep up the numbers if you Dis everyone . The Catholics per Pope says no rubbers and more babies but you people with a cult that is declining because of stupid ideas like this are  not progressive . You already have the internet showing the young how stupid christianity is and who's to say being two Christians bonded is best or one spouse won't turn the other gay or WORST into a Atheist .

 You act like being a Christians means Staying a Christian and you might want to see some older people who will tell more older people leave Christianity than join .

 Guess what - Plenty of Seminary Teacher become atheist . Askem WHY ?

Sure . Everyone loves Atheist

the bible says not to be unevenly yoked which means not to marry someone who does not share your beliefs. If you do, you will have hardship

"Be not unequally yoked with unbelievers." 2 Cor. 6:14.

You are correct. God,through His word is clear on the subject. 2 Corinthians 6.14-16 says,14."Do not be unequally yoked with unbelievers. For what partnership can righteousness have with wickedness? Or what fellowship does light have with darkness? 15.What harmony is there between Christ and Belial? Or what does a believer have in common with an unbeliever? 16.What agreement can exist between the temple of God and idols? For we are the temple of the living God. As God has said: “I will dwell with them and walk among them, and I will be their God, and they will be My people.”…

Maybe yes and maybe no.

Let's say the guy is the athee-evo.  If he pulls the girl away from her Christian faith, then she shouldn't marry him.  That would be unequally yoked (2Cor 6:14).  But if they can't keep their hands off one another, they should get married (1Cor 7:8-9).

Of course it is. 

Christianity exists as a behavioral mechanism 

and an incontestable damnation of every wish, 

thought, pleasure, passion, and human action. 

Just as in Islam, Christianity wants to be the last word 

with regard to everything that you believe, think, say, and do.

Yes.  Paul explains.  When we follow Jesus, we are considered righteous, atheists are considered unrighteous.

Maybe she's not really Christian? 

She either IS or WILL BECOME lukewarm, lose her interest. 

But maybe it doesn't matter to her? 

You'll see in a few years, no longer your friend, not praying, on it goes. 

Best to drop this friendship if she won't listen.