Probably this implies she had been a prostitute, and many have assumed it was Mary Magdalene. This is unlikely, however, for Luke does not identify her, whereas Mary Magdalene is clearly identified just a few verses further on (Luke 8:2), and apparently was a woman of some substance (Luke 8:3).

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8