hey AirBornette,
I am not a believer in gym tread mills, as they give you a false sense of your speed and make it easier to kick your legs behind you given the momentum it is providing. Running on a trail or track is always best.
With that said, like any sport, it will take you time to get back into running shape. First thing you need to do is build your endurance, not your speed. As such, try going on a 20-30 min run. DO NOT TAKE IT OUT FAST, just maintain a nice constant speed (you will need to be honest with yourself about your constant speed level) for as long as you can. Once you cant really run/ jog anymore, take it at a fast paced walk for another 10 min. If you really want to be able to run, you need to go for these kind of easy runs at least 3-4 times a week to build up your base. I admit that I am a jump-right-into-it kind of guy, but doing easy runs only once or twice a week wont do much for getting your legs use to this kind of faster paced activity.
Doing the sprint the straight away, jog the curves on a track is good at building up tolerance to lactic acid accumulation in your legs. However, I am not sure if that is what you really want to be starting out with.
One thing that has always been of immense usefulness to me is to run with a group. If you go to any local runners store, they will have information about local running groups. These groups all have a wide range of participants from those who only walk, to those who are hard core runners- with everything in between. They help keep you motivated, and will typically put you in an equivalent pace group. I highly suggest you try out one of these groups. One group that is national is called The Front Runners-
www.frontrunners.org Check out their web site and see if you might like to run with them. They are in every major city, and I have run with many of their groups while I have been away from home for business or pleasure.
Your friends method of preparing for a marathon seems to be more geared toward a very novice jogger rather than someone trying to go be able to really run a marathon. However, all the more power to her for wanting to complete a marathon (I have never attempted to even do a marathon, all my triathlons and road raced were at most half marathons.).
I am going to check with a good friend of mine who was a high school track coach about any more advice that can be given to you. Ill get back to you within the next day or so.
Best,
LA