As long as egoistic behavior is the optimal strategy we will not see a significant change in behavior.
It can only be changed by changing the surrounding rules and conditions.
If everyone can't do it (bringing more luggage than will fit above you) then doing that seem like you're doing it because you're better than everyone else, which is offensive to most people for good reason. If her whole family had flown first class, that'd be a different story. (They'd probably still be annoyed at the family for basically cancelling out some of the perks of paying extra for flights, though.)
Maybe the airlines I fly are just the worst examples, but I frequently fly business/first both domestic and international and the overheads are always full, usually due in part to passengers not in that cabin.
As someone who customarily boards early (due to fare class or airline status), I can tell you one solid reason, overhead bin space. If flight attendants would ensure folks put their bags on their row and the gate attendants ensured bags weren’t too large, this would be less an issue, but I routinely see folks fairly early in the boarding process putting their bags in rows in front of theirs, even though their row’s bin is empty or at least not full.
The worst example of this was my flight a few weeks ago. I was the first to board that flight, followed by another customer in first class and her family. The woman proceeded to put all her kid’s and husband’s luggage in the first class overhead despite her being the only one in that cabin (her seat was via an upgrade, not that it matters). The rest of the passengers in first class (besides me, thankfully) had to put their luggage in the first rows of economy due to her actions which had a ripple effect down the plane. Probably extended boarding and deboarding time by at least five minutes, all because of what I’d call selfish behavior.