I think the idea is that she should be excited that you're excited, and happy that you're happy, not necessarily that she should be excited by the very code you wrote. (That said, you would probably not mind if she "returned your bid" or "opened a bid" by asking you what it did, how you came to it, and made an effort to appreciate it with you. It would probably be less pleasant if every time you got excited about some code you wrote, she just responded with an indifferent "cool"---if at all---while continuing to text her friends.)

Also, what exactly do you mean by your last sentence, specifically, "besides our own"? If, as indicated above, the idea is that both partners are happy in the other's happiness, and want to do the things that make their partners happy, and are unhappy doing the things that make their partners unhappy, what does it mean to "[maintain] hobbies and relationships besides [their] own"? Many people maintain hobbies and relationships aside from those with their partners such that they end up maintaining separation. Why is that necessarily desireable?