can my broody hen adopt chicks?

No. A chick has to hatch under a hen for her to accept it.

 

Actually many people have had great luck with putting newborn chicks under a broody hen. They do it at night, take away the eggs that she has been sitting on and put the chicks under the momma. You need to be there in the morning to make sure the momma accepts the chicks. Sometimes they don't and you need to rescue the chicks.

Now, your chicks are two weeks old already so that does paint a different picture on whether she would accept them or not. You could certainly give it a try. Replace the eggs she's sitting on with the chicks at night but make sure you are there first thing in the morning to be ready to protect the chicks if she attacks them.

 

Since I'm not good at "first thing in the morning" stuff, I "sneak" baby chicks under a broody hen late in the afternoon or early evening. That way I can sit and watch or at least remain within chirping distance and listen for a distress call.
I've been sneaking chicks under hens for a few years now. I like to put them in a box near the foster mom, so she can hear them, as she would if they were in the egg. Then I slip them under her one at a time, removing an egg each time (just in case they can count). I will often put in a couple of opened plastic easter eggs, so as to fake the broken egg from a hatchling. I have had two chicks scream out the distress signal in all this time. One managed to get stuck behind the nest box, the other was being beat up by momma. The one that was being beat up ended up with a severely crossed beak and I ended up tube feeding her. So maybe momma knew something was wrong with her and was going to cull it, as would have been the humane thing to do in the wild.