Head shot session with my girlfriend

The second one speaks to me the most.

I will agree with the others suggesting that you get a longer lens, and step back. Or keep the same lens, step back, and crop (which will give you the same framing as a longer lens). Or just keep the same lens, step back, and don't crop.

I use a 50mm lens for portraits like you (75 full frame equivalent), but I find that for most of my subjects, it's most flattering as a head-and-shoulders portrait lens, rather than as a facial portrait lens. Filling the frame with the subject's face will cause significant perspective distortion (like we see here).

Perspective distortion can be used artistically, but for a beauty portrait I suggest reducing it by stepping back. Give her some more room to breathe within the frame, don't always center her in the frame, and I think you will like the results.