Use hair conditioner!
Most any conditioner that moistens real hair can do great things for synthetic as well. Give it a wash, brush through a good amount of conditioner and let it sit for a while, then wash it out. Easy! I like to use leave-in spray conditioner afterward, too, just to give it an extra moisture seal.
For re-waving her hair, get it wet with warm water, then curl bunches of it around straws and fasten with bobby pins or clips, like this:
(I like to wrap strips of paper towel around the hair first before clipping it, which helps keep the hair together)
Let it get bone-dry for at least 24 hours, then remove the straws. They'll likely be way too tight, so lightly mist them with water and brush them gently, and they should make nice wavy curls.
You could also loosely braid her hair while wet, then let them dry and that'd made waves, but I think that would produce a bit too crimpy of a style, compared to how she looks out-of-box...
Good luck with styling!