Be gentle with me - not been on here for ages 
On Sunday we drove 130+ miles from where we live to the coast (me, DH and DS). Knowing that my cousin lives 40 odd miles from there I mentioned to her earlier in the week that we were thinking of going. She text me the day before and I could tell from the questions she was asking that she was up for it, so I invited her and her partner to meet us there. She text "I am thinking along the same lines, but (partner's name) not that spontaneous so we will see". i phoned her and more or less arranged to meet her in Brighton.
Anyway on the day as I was hurtling on the M25, she text that she was "not sure about our plans for today, enjoy Brighton". I just assumed from that she wasn't going as she had mentioned how crowded it would be and traffic, etc, etc. We had a great day there despite the fact they did not come. We stayed in text contact that day and she said they had done a lot of gardening that day but nothing else. I told her we had a great day.
So imagine my surprise yesterday (Monday) when she texts me and says "We are in Brighton today! We are going to have a coffee and just about to go on the pier" WTF? 
So I texted back "Oh. I don't know what to say since there just yesterday and invited you and you blew us out. Will try not to feel offended". She has not responded.
But I do feel offended - so AIBU?