Suspected slander.... Can I be sued?

I have been having problems with a member of staff who was haring me over texts about overtime. I sent a text to a work colleague calling her a "cheeky *****", which she saw. She is now stating she is going to contact a solicitor. Can anything happen with this? I was under the illusion as it is an opinion ( freedom of speech ) nothing will happen. Am I right, or should I be worried??