Could i let her sit on them instead or should i continue incubating them???
If she is still broody and is sitting on a nest, yes she will accept the eggs. Put them under her in the dark of the night when she is drowsy and you should be very happy with the results.
I rather her sit on them. She's in with another hen and rooster, will they bother her if she sits on them?
You are dealing with living things, so anything is possible. However, I would not hesitate to give her the eggs. It is possible the sebright will lay in the nest with her, so you need to mark the eggs she is sitting on (a magic marker of soft-leaded pencil will do) and daily remove any new eggs the sebright might lay. It is possible the sebright will break an egg getting on or off the nest if she lays eggs in that nest, but the broody could possible break an egg getting on or off the nest herself. I think this risk is low.
If the eggs that i want her to sit on are not her's will she still sit on them????
Absolutely. She will accept a golf ball or wooden egg if you give them to her.
Many people advocate isolating a broody to where the rest of the flock cannot get into the nest with her. There are some advantages to doing this, but I do not consider it absolutely necessary.
I just saw Scooter147's post. There is a risk of the hen getting confused and going to the wrong nest. It does happen and this is one of the reasons to lock the hen up away from the rest of the flock. I don't agree that there is a good chance that will happen, but it certainly does. There is a chance that by locking a hen up, you will cause her to break from being broody. Especially with a silkie, I would not expect that to happen, but there is a chance. With living creatures, you can not be sure of anything.