Realistically you'll probably need to run 3 (maybe 4) times a week, one of those increasing in distance and the others some kind of intervals and/or tempo running.
Cycling will benefit your endurance, but you'll still have to switch focus. It's probably going to be the long run that's the hardest to make time for. If you can do that, you can do it.

You'll probably have to start training 2 (maybe 3) months beforehand, too, so it will be through the late summer. The advantage I suppose is that up until then you can increase your running-as-cross-training and then switch to running more later.

Tough decision, but even if you decide not to do it, you can meet up and cheer her on - a cheering squad is always much appreciated.