So last year, you offered to take her out on 2 day trips, where you didn’t ask for a contribution, and she didn’t add to your costs.
On one trip she paid more than half for lunch, and on the other she paid for all the kids’ ice creams.
So in both cases, she cost you NOTHING but made a nice token “thank you” payment.
For Scotland, YOU offered, and YOU didn’t want a contribution. Until your husband told you off.
Again, she didn’t cost you anything. Well. £2. She paid up what she owed you. If that was cash, I can see that friends would knock £2 off if handling notes.
She suggested petrol contribution, but how did you respond? Was it a, “yes please”? Why didn’t you say, “could you do £20 towards this fill up now please?” So often there’s a dance around offer and refusal, or at least not taking the offer up. Given that you didn’t initially want a petrol contribution, did you actually accept her offer?
Even the comment about where you’re going next is easily just friends joking around.
Of course she COULD be taking the piss.
But equally, it’s telling that you were fine until your husband decided to disagree with you.