You might do better asking in the Triathlon forum but I know what you mean about it being difficult to find plans.
I just make up my own plans. The biggest problem most people have with swim training is the boredom factor, so it helps to mix it up with a few different drills. The drills available will depend on what stroke(s) your friend does. Because swimming effectively is very technique driven and not so dependant on fitness, the more often you can do it, the more quickly you will improve.
If you google "swim drills" you will have more luck finding information in open access sites.
Ultimately though, the most straight-forward plan is to draw a graph showing how many lengths your friend can swim today versus how many she needs to swim in eleven weeks and aim to increase the weekly distance proportionately. There's no need to taper like you would expect to for running.
I hope this helps. Wish her luck.