Unlike most "anyone can run a 2:30 marathon" letsrunners, I'm fine with people "running" 5, 6, 7 hour marathons. More power to ya. And if you have cerebral palsy or severe injuries and want to do a marathon as a challenge no matter how long it takes, go for it.
But good grief, I would think that if you took a totally sedentary but not disabled, 300 lb, 40 year old woman and gave her a good pair of shoes and some tubes of bodyglide, she could go out tomorrow and do a 5k in under and hour or even a marathon in under 10 hours. The marathon wouldn't be easy and would wipe them out for a week, but with determination they could do it.
Is this woman also disabled? I'd bet there are other women her size who can move better than she can but don't make a big deal out of it.