You've given yourself the answer in your title
Depending on your practice, I'm not Wiccan so not fully up to speed on Wiccan rituals, set up as you normally would for spell casting.
You'll need a mirror (a small compact mirror will do), draw a protective symbol on the back of it (pentagram, rune or sigil).
Place your intention into the mirror (you can look up a 'return to sender' spell or create your own).
Put the mirror in a window facing it outward so it reflects outside.
This reflects the other persons ill intentions back to them.