If an ex-bud does a service as a free gift can they report against your credit that you didn't pay a yr later?

Last year I was friends with a woman who owned her own tax office. Naturally, when tax season came along, my husband and I went to her. Upon finishing filing our taxes, she said she wouldn't charge a friend, so we didn't have to pay her. Then, after a year of horrendous mood swings and alcohol consumption, my husband and I felt it best to part our ways with her. Unfortunately, she has recently started texting my husband out of the blue wanting money (not related to the taxes she filed for free, but for no reason at all. ?I know, right?). When we refused she got angry and sent, "Well I have a contract with both of your signatures that says I did your taxes last year and didn't receive payment and will report this against your credit" We're not really worried about this, but I am just so curious as to whether she could actually do that. Is there a time limit for filing a strike against someone if it has been a full year? Can someone do a service for free, have a falling out, and then deal out threats? Would this even go through? Once she realized we weren't going to just give her money, she didn't even demand payment for that service so I don't even know how much we would "owe" her. Just straight to the reporting on our credit business.