Do the other chicks pick on it? Maybe you could take another of the 8 chicks and put it in with the other as a brooder buddy so it won't be all by itself. I don't know... When my mama hen rejected her 2 late hatchers, I had them together in a brooder until I rehomed them along with 5 other...
Keep trying to get to her. But, you may have to trick her to do it in a timely manner. When my chickens run under the coop, I use a long board to guide them in the direction I want them to go, usually into a container of some kind. If I move slowly, it doesn't scare them too much.