Is it okay to be friends with Wiccans?
To clarify terms, we should note that Wicca is a form of witchcraft, and those who practice it are called Wiccans. There is nothing inherently wrong with friendship between Christians and those who practice Wicca, but Christians should take care not to be drawn into practicing any occult rites with Wiccans. It may even be prudent to refrain from joining Wiccans for social celebrations of Wiccan holidays, even when Wiccan rituals will not be practiced at the celebration. (For example, some Wiccans open their homes for social celebrations of holidays such as Yule, in much the same way Christians invite over friends and family for Christmas parties.)
For more information, I recommend reading a booklet I wrote, 20 Answers: Witchcraft & the Occult.