The uniform standards for the airline I work at specify that tatoos are not to be visible. It is acceptable to take care of this by placing a flesh-coloured bandaid over ankle tattoos and the like. It is fairly common to see this on the line.
As above - the industry hasn't gotten to the point where outside courses mean anything (luckily!). ALL airlines train ALL recruits to their own standards, so taking a paid course is a waste of money.
You may find, however, when you check the application requirements, that an accredited St. John's First Aid certificate IS a requirement. The nice thing about paying for that is that it is a useful addition on your resume for ANY job she applies for in the future, as well as being able to use it as an example for showing enthusiasm and dedication at the interview.
Training courses - St John Ambulance