Evan's gambit declined

I recently played an online chess match against a higher rated opponent using the Evan's Gambit. She declined and I was baffled about the situation. My questions are:
1. What's the best move if the opponent declines the gambit?
2. Is it better to decline the gambit?
3. Do you still follow the same principles if it's declined?

Here's the game btw:

I imagine you played 7.a4 with the intention of playing a5 trapping the B. That was why 7...a6 was played.

I figured that out as soon as she played it. It gave the bishop room to move.

Try 5.a4 I don't know how 5.c3, which blocks your knight, is keeping with Evans Gambit principles.

If you play the Evan's gambit you want to play c3 then d4. I studied this before playing.

There is an in depth analysis of this gambit on Gambit gang forum, just search for Inside Evans gambit :))