In Ontario anyone can go online and get a food handlers certificate from the Canadian Institute of Food Safety which is good all across Canada. All employee's of a food service location I suspect over the next few years will be required to have one to work in the industry and that includes the front of the house, that's what I'm hearing and it makes sense. Maybe check in your area if something similar is available.
Anyway, as far as culinary schools that give out certificates/diploma's for just online training I suspect that doesn't exist, for obvious reasons. I'm a big proponent of methodology, food theory, culinary history and taking online courses could encourage a discipline that otherwise might not get accomplished, so maybe if it's a good course and are not just trying to take your money. Have someone you know look at the course that has some experience in a kitchen and is competent to take a look before you slap down the credit carb, just an opinion.
From a quick search it appears that "The Escoffier School of Culinary Arts" does have accredited online diploma's and degrees in conjunction with an externship which I haven't looked but would require your stepdaughter to work in a kitchen and it's generally for a certain amount of hours.
In Ontario the chef apprentice program
to become competent in the trade of Cook, which is a prerequisite for the Chef program, is 6,000 hours (approximately three years) consisting of 5,280 hours of on-the-job work experience and 720 hours of in-school training.
This of course is the paper trail required by pretty much all large corporations like Disney, the Hyatt and other large hotels and cruise lines for example and is pretty much needed to get a job in these places, simply because it's mostly a factory production line and having a standard like this minimizes labor costs while maximizing profits, it's a business and you are required to know or your replaced, but it can be for the few that are truly gifted a stairway to a fulfilling career, even in the quagmire of uniformity the cream rises to the top.
I'm not trying to talk you out of this, but it's not like it's portrayed on TV, it's a grueling and ruthless job where 80% quit. Most don't make it out of culinary school, professional cooking at the higher levels in not a cake walk, and considering your stepdaughters limitations I suspect this isn't in the cards but taking online cooking classes or night school culinary classes locally once or twice a week supervised by someone like yourself might be something to look in to. imo
All that aside, does it make a difference when applying to a small independent restaurant if someone has these credentials? Not for me, I couldn't care less. What I'm interested in is assessing a prospective cook and employee on how they move, handle simple tasks, time management, personality and the fit in the kitchen in relation to other employees as well. I get all prospective cooks to do a stage for generally 3 days and only then do I make a decision and of course it depends on the job they're applying for that determines their qualifications and requirements.