My gf (muslim) and I (atheist) want to get do nikah privately, anything we should know?

My gf isnt very strict practicing islam but its a huge part of her life and she respect most of it. Obviously we are dating (got intimate too) and together as we fell in love instantly and cant help it.

We are pretty certain that we want to get married, but the soonest is in 1 year, which is when she is done with her study. At first we planned to do the nikah in her hometown (with her parents) and then officially for the law with the whole paper signing shebang.

But she feels bad for breaking the rules. So we were thinking to do the nikah privately without anyone knowing about it. Just the 2 of us and 2 witnesses. And later when she is done with her uni we do the nikah again in her hometown with her parents and go public.

Obviously now there are 2 problems, should i convert and do the nikah or only do the nikah and lie that i already converted. Personally i dont mind converting but i cant say i believe, maybe in the future but not right off the bat.

The 2nd problem is, can we even do something like this? Do 2 nikah? As far as we know you dont have to sign anything so nobody will find out but still... Should we even do that?