Why is Erika treating me like a baby?

At work there is a new supervisor and her name is Erika. I know what to do and have been at the company a long time. In fact, I was on my break and she was on break with me where I always know to go back to work in time. The other day she came over to me while I was on my phone sending a text message on my break and she said to me: “Ok. Are you ready now to get back to work? Come on. I can walk you down.” I looked at her weird and told her I still have time then she kept standing over me and asking me if I was sure I was following the rules. Why is she treating me like that and escorting me to work with keeping an eye on me for?