I can't figure out the etiquette here. Family day out with kids and a grandparent. DH buys all the train tickets and hands them out. They weren't at all expensive, DH invited grandparent along, outing was his idea. It never crossed his mind that GP would pay their own way. When we have days out we always pay GPs way and never make any reference to it. It's really not an issue. I noticed GP had transferred the exact sum for her ticket (£12.10) into our account and she never said a word about it. There is no financial reason for this, we are thankfully entirely able to afford her train ticket, and to pay for her lunch etc. I think this was a bit rude really but I could be wrong!
In the interests of not drip-feeding, we have many issues with said grandparent (MIL) and she has always been somewhat passive aggressive and narcissistic.