you have 2 options: the banked 400k or proof of monthly income coming from outside Thailand. I think that number is 45k... Better check with any Thai embassy website, the numbers are the same for everyone.
it's not about getting a job, it's about getting an ED visa. Most Muay Thai fighters make peanuts too and knowing Thai isn't a career option, but one can get ED visas for those.
well, people can get one for Muay Thai or self defense... If they provide it for those, I wouldn't be surprised if they provide one to become a dive master.
With the current rules, at no point in time, BUT, Thai immigration could decide at anytime that an overstay could affect her chances of getting a visa in the future. Furthermore, an overstay here could affect her immigration status in other countries.