Could this be slander?

No. What you stated was opinion. Slander is so difficult to prove, and most State's have such narrowly defined Statutes, that the other person would have to prove that you had damaged her reputation to the point that her Friends, and other contacts were no longer ociating with her. Also, for her to get a judgment for any type of monetary damages, she would have to specifically prove where she had lost money, to the penny. As for punitive damages, most states also set caps, so that punitive damages can not be compensatory.