With living animals you never know how old is too old. Anything can happen. I would not try it but it could work.
Some hens will try to adopt any chick, even that old. Most will not. In a normal situation the hen and chicks bond and imprint on each other, starting even before they hatch. The chicks start peeping after internal pip to let the hen know they are coming. They bond some more while they are under her. When she leaves the nest they want to follow her.
With chicks two weeks old they may have imprinted on you or something else, certainly not the hen. Even if the hen wants them, they may not want her. Sometimes she can bully them into accepting her by pecking them, often she won't try.
Another aspect is that it sounds like she just went broody. I've had hens that just went broody accept new chicks but I've also had failure with that. Sometimes a hen does not kick over to full broody mode immediately, it may take a few days. I don't know which category your broody falls in but that is an added risk.
You can always try, you might strike gold. But I would certainly have a plan B ready.
