I believe that it is important that companies advertise their vacancies well, however I can't say I believe in targeted ad campaigns. My take is that if someone has the true passion for a career, they won't need to be told to consider it, they'll just get on with it and apply.
My cousin (who is female) considered a career flying airliners but when she saw the cost she walked away, despite the fact that her parents could have afforded the training. So if the airlines to bring back the Hamble days (but with women allowed to apply) they might get more female pilots.
I don't think the £300 assessment days for a mentored airline gig are a great motivator either, train driving roles are often 100 applications per job and yet still the company pays.