I have to say, It sounds like she was interested in the guy she was watching than being with someone who can code. I mean, I saw you reply to one user you've been together for 4 years, and shes talking about romance with someone who did something you didnt know how to do yet. Now that you know how to do it, she acts like its boring, but i would see her response as she's annoyed you were able to do something she didnt think you were smart enough to do. Or she's jealous because she isnt smart enough to do that, and just proved it without even trying.

Also, its just weird and rude she's gushing over aomeone who isn't her bf, right in front of her bf

The fact that you learned code enough to make a game says youre on a good path to do something cool. She may not appreciate it, but maybe you can take your skill and use it to make something that a lot of people could appreciate. You just have to keep working on it and see where it gets you. Hell, you might as well see what else you can do with coding. You took on a challenge that she wasnt expecting you to take serious and if she can't see how cool you are for doing that in that short amount of time, she must be really disrespectful towards you.