On Sundays my mum and I often go out for lunch. We sometimes go to church first then we go home to her house (in separate cars). Then we go wherever we've decided for lunch.
Usually we have discussed and booked this ahead of time. Occasionally we haven't been organised enough but we will ask each other on the Sunday morning if we fancy going out for lunch. We can then decide the specifics of where we're going closer to lunchtime.
Neither of us had booked anywhere for today, we hadn't discussed it previously and it wasn't mentioned this morning either. I assumed that, as we hadn't made plans, we weren't going out this week (and added to this assumption was that I had spent the day with her yesterday). I went to church this morning and when it was over, some friends told me they were going out for lunch and asked if I wanted to join them. I said yes and had an early lunch with my friends.
The issue is that I have just spoken to my mum and she is very annoyed that I didn't tell her I wasn't going out with her today. She says she waited on me and it would have been good manners to tell her because she has a life. I replied that I'm sorry she waited but as we hadn't made any plans together, I hadn't thought it was necessary to tell her I had made other spontaneous plans. She thinks I have treated her badly and is still angry.
Who is being unreasonable?