My husband & I tip based on the performance of the wait staff. If the food is especially lousy, slow or wrong, we will let the manager know, but not penalize our server.
In your case, you saw her repeatedly checking on your order, being attentive to letting you know, and otherwise taking care of you. One thing she could have done in addition, was to get her manager involved. But still, she wasn't dropping the ball in trying to make sure you got good service. So your tip was appropriate.
As for the wait-time, I think 15-20 minutes is adequate. Sometimes they have to juggle orders around the cooking surface, or wait for more supplies to be prepared, so they will put other orders in front. But overall, if you saw other people getting food before you, who had ordered after you, & your order wasn't complicated, over 30 minutes is a bit excessive, & I would have been proactive & asked to speak to the manager yourself.
BTW, we also notify managers when we have had an outstanding experience, in addition to leaving a good tip! T. :)