Having done a marathon or two I would advise she uses the Concept 10
or 5k training programme. Lots of variety in there to keep her happy
but important she does one or two 10 milers prior to the half
marathon. Late March is plenty of time to get ready and i was unlucky
to have to do a 18 mile training run in the morning prior to doing the
Kingston Head in the afternoon one year.
Time on the water is the same as time on the Concept. Dependant on
distance from your club I found the easiest way was to run to and from
the club to keep the running legs going.