Mum constantly on my back over small matters

Any little thing my Mum has to blow up out of proportion, which makes her annoyed with me, and me with her. I try my best to avoid any confrontation with relatives or friends.

One example, I was on holiday with her recently. On an organised tour, we stopped of at a place that had a souvenir shop. The group had a look around. When it was time to get back on the bus, we left the shop.

My Mum and I both went out at the same time. However, I turned to get on the tour bus, and my Mum went over to speak to another member of the group. I got on the bus and sat down, not on the seat that we were using before as there was another couple there. When my Mum got on the bus, she went straight passed me. When the driver asked if there was someone missing, without me realising, my Mum piped up and said I was. The driver got off to look, then my Mum came up behind me annoyed. When we arrived back at our accommodation, I thought it was over and done with. However, when we got to our room, she became sulky (Like she normally does) and said that I made her look like a complete chump. Thankfully, things cooled down over the evening.

Does anyone else have this?