If she's not on a leash or long line, keep her on one. You will need to do that for at least 6 weeks. During that time, work on the attention exercise as well as recalls. Call her to you the minute you see anything she even might chase. You need to develop a split-second response to your calling cue. Remember, Border Collies are bred to be able to do that!
Read the articles I wrote on Attention, Please! and the one on Barking at the link with my name below. Titles are in alphabetical order. Though she's chasing and perhaps not barking, that method will work.
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Kathy Diamond Davis, author, "Therapy Dogs: Training Your Dog to Reach Others," 2nd edition, and the free Canine Behavior Series articles at http://www.veterinarypartner.com/Content.plx?P=SRC&S=1&SourceID=47