Yeah, us humans can only do so much to replicate what a mother hen would do. Chicks don't have pasty bum when naturally brooded, but with us it's different. And like Abriana said, it's not a huge sickness and you don't need to fear too much. As long as you check her regularly and clean her bum when she needs, she'll be fine.
Also, to help her get more human friendly you can feed treats out of your hand, sing or hum to them, or hold them. However, be careful with holding. If you stress them out, it won't help. Try to do things inside of the brooder so they don't get so freaked out about a disembodied hand reaching in and taking them from everything they know (from the chick's point of view).