You say that this girl is approaching someone else.
So, first…find out if she is already in a relationship. If she is, then leaving her alone would be best.
If she’s not in a relationship, then…BEFORE…you even decide to start contact with her…you need to decide if you will be able to take things to the next level if a relationship develops with her. If you still can’t take things to the next level, then it’s a waste of her time and yours…and that would be like leading her on (in the event that she develops a mutual interest).