>...without her knowing would be crossing that stalker line

The boundary between courting and stalking is blurry, but make sure not to come off the wrong side of the line. Your intuition is correct, however you must not lazily stop at the first conclusion, but react to it: if you're joining an event to which she takes part, it's because you have a reason to be there, so it's your job to find out which one it is, or engineer it. Same goes for an event that you organize. You organize an event to which she takes place because you did your homework and know that she comes to this type of meet ups, or has a reason to do so (hint: birthday parties). No live contact, no girl: this is where the buck stops, hence the beginning of your thinking.

>I don't really want to involve [my friend] further in this. Is there any other way, or is [...] having her as a intermediary the best way?

Don't overuse your friend, limit yourself to information gathering or critical stuff. Having more common friends is a good idea. Keep it subtle.