Now she has to be not only a good coder but a great one, (and in a tech stack she didn't had used already).
Otherwise, a year from now, they might not feel so charitable, and the story will be "from director of design to fired IC".
A friend of mine made a similar mistake once, believing the BS of the "parallel management and engineering tracks".
To make your assertion requires far too many assumptions for you to know whether this was an act of "charity" or not.
People are with more than their paper skill sets. If this person had been working at Stack Overflow for years, then she probably knows far more about the company itself than a new CS grad. That can be a huge asset. Likewise, her experience of being a manager of the Production Design team, and the Director of Design, can be great experiences to add depth to the development team.
I am a senior software engineer. I am far from the best programmer on my team. A new CS grad could probably out-whiteboard any CS problem thrown at me. But my knowledge of 12 years of the company's development history, my gut-understanding of what kinds of decisions are good for the company, my ability to communicate well with product owners and elicit the right kinds of information and foresee design problems before they happen all contribute to me being an invaluable member of the team.
Three years later I was making more $$ as an IC with none of the stress and nuisance of management.
Five years later I was making 2x my old salary and significantly happier w my day to day work.
To each their own...
I was a good tactical/operational manager but did not enjoy many aspects of the job (bureaucracy, performance reviews, personnel problems, being 'corporate'), had limited interest in strategic business concerns, and did not have the enthusiasm needed to move up the management ranks.
I'm much better suited to being an individual contributor.
It is a risky move and not one I would recommend to anyone - but it is one I‘ve done myself (incl. pay cut) to get the experience to boost my career. Also keep in mind that careers span decades and while specialization is sought the landscape does shift (sometimes quickly) and diversity of skills can provide a degree of robustness.
And yes, the career track slides are not a foundation on which to base decisions.
Besides, it's not like software engineering doesn't pay. Even before I landed by current SV big tech job, I had more than made up for the initial paycut I took at a local startup.