Ive used jealousy a couple of times and pulled girls into STR and LTR. (More STR because I seem to have a problem with commitment and duck out within a couple months normally). They were digging me anyway though so Its not really a solid answer. Definitely makes them a little insecure about where they stand with you.
I used to run a bar and was therefore being paid to flirt with chicks - Any girls I was seeing came in, they would instantly look worried. Poor girls worked hard to keep me, but free spirit that I am, I liked to take advantage of my options
Sorry, rambling. basically a little jealousy will do you no harm. Make her compete - or at least feel that she may have some competition. However long the relationship lasts isn't going to change just because her interest level spiked over a little jealousy.
All things have a time limit, dont go worrying about how long it will last - just ENJOY WHAT YOU HAVE WHILE YOU HAVE IT.