An iPad Air 2 is capable of supporting sound in/out via either the 3.5 mm phone jack or the lightning (aka charging cable) jack. I'm guessing that she is using the phone jack, and has just found one of the big reasons Apple eliminated it on the iPhone 7: phone jacks are ancient technology, and frankly prone to problems.
She should be able to get satisfaction via either bluetooth or the OTHER jack. Apple not only offers earbuds for the lightning jack, but also an adapter for the lightning jack that provides a 3.5 mm phone jack for the benefit of folks who can't bear to ditch old-but-still-working earphones.