I switched careers too and I can tell you that the first job is the hardest to get. Build a portfolio and network hard. Take contract jobs. Do whatever it takes to get your foot in the door.
I learned to code at 28 and have been doing it professionally for 10 years now. Coding is easier than it used to be. I don't think an age limit applies.
If someone goes to grad school, especially if they had 2-3 years of full-time work mixed in there, they can easily be pushing 30. I basically did a career change at about that age into the computer field as a product manager.
my initial couple jobs were as a software engineer so yes. these days I do a blend of coding and marketing, as a developer advocate at AWS. good luck to your gf, pls feel free to send more qtns I think my email is in my profile.