Give her a set period of time where she can "have space" and not have to talk to anyone else if she doesn't want to.
This worked really well for my younger brother growing up. He would get dressed, come down, eat breakfast while trying his best to be civilized, make sure that he had everything ready for the bus, and then he could camp out on the couch by himself and zone out in front of the TV until it was time to go.
Knowing he would have that "alone time" before the bus seemed to help a lot. If nothing else, it motivated him to get his act together quickly so he could disappear for a bit.
By the way, now that he's an adult, coffee seems to help a lot. Or so my sister-in-law says.