So, to clarify, you're worried that her success is going to trigger jealousy issues and frustration on your part when she loses faster than you?
And she's in a different city than you? What kind of help is she looking for from you? Just a check-in buddy?
You can always refer her to 3FC and suggest she get support from here, and you can still keep tabs on each other through the site... but maybe it won't feel as personally competitive if you're not working with her one on one. She won't necessarily feel the need to crow to you (or brag to you, as you might take it if you get competitive) about all of her losses if she's able to do it to everyone on the forums? Not to mention, when you're working hard at focusing on yourself, sometimes it may not be better to be keeping tabs on, and trying to advise someone else at the same time. Sometimes it's nice just to worry about your own journey.
But if I were you, I'd just try to put things into perspective. Even on the forums you sometimes get a bit jealous if you're the same height/weight as someone else, and you're keeping tabs on each other... and they start rocketting past you in losses. It's happened to me often.... I usually feel that I simply need to re-channel that jealous energy. What it comes right down to is that... it's not a competition. You can't and shouldn't compare yourselves to others, because everyone's body is different, and is going to take the weight loss efforts differently.
So, when I feel jealous, I try to re-channel that energy into myself. I look up to those people who are doing well. I ask what they've been doing, I take advice, and I throw all that energy into my own journey, and pushing harder for what I want. I've got a finish line in mind, and it doesn't really matter who beats me there, just that I get there in the long-run.
Essentially... if your friend's bigger, and she loses faster, well... so what? So what if she loses 40 lbs, when you've only lost 30? You've still lost 30 lbs! Nothing she can do can diminish your accomplishments! And the RATE of weight loss is really irrelevant compared to what your goal is, and and how hard you're working to get there.
Try not to stress honey! Good luck!!!!