Kato -the race information for Sunday says that you should, as part of your training, been able to run for 6 miles continuously . Do you know if your friend can do that?
There is no Maximun time to complete the race, but there is a sweep bus at 17 minutes per mile. Aftre that, runner will have to finish the Race on the pavement, as they will reopen the roads . But she can continue and will get a time(unlike in many races ).
If she is planning to walk the whole course, she will probably be about 20 mins per mile.
Given that she is very overweight and unused to exercise, has she taken medical advice on whether or not she is fit to walk /run 10 miles?
Personally I think it's utter madness, but I realise I'm the grumpy old woman of this thread