Broody Hen hatching purchased eggs

[terriminx]

One of my hens started spending longer and longer in the roost to lay her eggs to the point where in the end she stopped leaving it. I read up and realised she was broody. As I only have 2 hens (Brahmas) and only a small garden, I decided to get her a couple of silkie eggs to sit on. If they hatched they would be small enough to fit into our situation and if they didn't, my hen would have had something to sit on in her weeks of need.
Now I have just one thing worrying me. Does the hen sit on the eggs for 21 days or is she broody for 21 days? Am I going to have to keep an eye in case she walks away from them before hatching and have to incubate them? I have the equipment but as you can guess I am new to all of this. Obviously, by the time I realised she was broody and then ordered the fertile eggs, I guess almost a week went by.

 

[chickens really]

She will set till the eggs hatch. Although once she weans them they may not like Silkie Chickens.

 

[terriminx]

She will set till the eggs hatch. Although once she weans them they may not like Silkie Chickens.

Thanks. You’ve put my worry to rest. I’ll let you know how it goes.