1) Sunk cost fallacy.
2) What else are you going to do when all your training is academic?
2) What else are you going to do when all your training is academic?
As for why she does it?
>> Sunk cost fallacy
I'm assuming this is based on the phrase "those who can, do; those who can't, teach". That all of her time has been teaching, so she might as well keep teaching. I'm also assuming you've never met someone who is actually passionate about their work. Is willing to work at 70% salary because funding is tight, or will take a pay cut to do something they love versus something they have little emotional investment in.
>> 2) What else are you going to do when all your training is academic?
I'm assuming here that you've never talked to anyone concerning their experience in getting a PhD. While many go on to academia, very little do it specifically to teach, many enjoy the prestige, pure research communities, and subject matter they study.
What the parent comment was saying, and something I'm quite familiar with, is that when you have invested a lot of time and money in getting a Phd, and then find the job prospects slim to none, you are likely not to just give up and take a different job outside your field because you have "sunk costs" into becoming an academic. Thus, you may take a job as an adjunct in hopes of getting to be a professor someday, even if your economic position may be better to just get a job in industry somewhere.
What's the alternative? Flipping burgers for the same pay?
Or do you imagine there are tons of industry jobs out there for folks without experience.. who will probably be considered overeducated but underqualified?