To get them to drink from a bucket get them sucking your fingers and lower your hand into the bucket so they are sucking up the milk, they soon catch on.
The important thing is to get her a companion. She needs an older quiet horse to 'adopt' her and teach her horse manners.
Problems arise with bottle fed foals is because they demand food and the human never disciplines them as a mare would. You really have to be very strict with yourself over correcting the slightest misdemeanour, firmly and fairly.