How do I tell my girlfriend I would like her to be more muscular?

I really am into muscle girls, I mean big bulging muscle. I don't have an upper limit but I have a lower one: https://imgur.com/WLAzSOU
I would love my girlfriend to be a little bigger like this maybe or even bigger:
https://imgur.com/qCRkTFw
She currently looks somewhat like this girl but with better abs and lower bodyfat:
https://imgur.com/RU8DOmf
I don't know how to ask her. She is still working on her body but doesn't seem like she wants to grow bigger (I haven't asked her).

So my question is how can I tell her that I would like her to grow a bigger?

P. S. Don't start with "I don't know why you would like that, she will look like a man blah, blah", is personal preference, besides that she likes having pumped muscles