It's generally not cool to go right ahead and buy someone something from your own hobby, because if they're not into it they have a balancing act of not offending you but also expressing they don't like it.
So start with telling fun fluff stories if any are related to her interests. Build up from there.
tell her you'd like to play with her, tell her to give it a go, flick through the various armies and explain how they work. proceed from here.
My GF really likes the inquisition and I play eldar so for her starter she asked to go 50/50 with me on the Death Masque game, figure it'll be good because it has a 'story mode' as well as a little rule book and some really cool miniatures.
Chaos. Try Slaanesh, might improve your fun in other ways...
I got my ex into 40k via nids. She loved those hungry fucking bugs
What's up with that? Does the idea of hivefleets birthing forth vast armies that later return to the womb trigger the maternal instinct?
Probably because they are pretty much the only asexual army. Well, maybe tzeentch too.
I think it's more about them being "cute" critters rather than soldiers. It's like collecting cats or something.
but user what's cooler than the human spirit made to combat?
tiny critters apparently
For the most part, women relate to the Tyranids because women are ravenous monsters who only exist to consume. After they have drained you of everything, they will leave and find another victim and repeat
Or they're just cute. My ex found rippers adorable.