Binoculars for s/o?

For mine and my girlfriend’s 2 year anniversary, I wanted to get her a pair of binoculars. Although she has been obsessed with birds her whole life, she just recently got into birding, and she doesn’t have her own pair yet.

I’m not a huge birder myself, (although i do enjoy going on birding walks with her), so i don’t know much about all the different gear.

I’ve been looking through this sub and decided to purchase some from the vortex brand. I’m between the diamondback 10x42, triumph hd 10x42, or the crossfire hd 8x42. From what i’ve read, the 8x42 size seems to be a better fit for her, but i’ve also seen a lot of people rave about the diamondback line. Any thoughts and opinions would be greatly appreciated!!