Is this offensive?

I used the men's bathroom at the corner store in the gas station because I really had to go and someone was in the women's. Anyway, some woman was there when I got out asking me if I identify as a male. She said unless I identify as one I am being rude using the mens bathroom and inconsiderate to the transgender community. I never told her if I identify as a man or woman. I just smiled at her and told her to have a nice day. We didn't get into it. But anyway I always do that when I need it bad and the bathrooms are the private 1 stall kind. I don't really feel the need to use my gender assigned bathroom in general but I do if it's open. What do you think? Was she just crazy?