I did it in 2013. Training should involve hills as the route has about 500m ascent & descent, also running on mixed surfaces footpaths, rocky tracks, tarmac, smooth paths etc. Make sure to train in the shoes that’ll be worn for the event.
I struggled for 2 reasons, it was 25? and the idiots who organise it cocked up the course so we ran 14 miles not 13. They moved the start/finish from the school to Coniston Hall farm but forgot to tell the competitors about the extra distance! It messed up the marathon course too.
Beautiful race in a great location but Lakeland Trails will never get another penny from me. I know the area well and the event signage on approach was appalling. Most stewards were really nice but there were 2 awkward ones (maybe the heat fried their brains). I thought overall they were pretty shoddy. I’ve done a few trail races in the last 7-8 years with them but never again. They’ve grown too big and seem to have lost the fun, friendly approach.
I hope your wife enjoys it and good luck with the training.