This happened last night and it’s playing on my mind. We went for a meal for my Dads birthday, me and DP couldn’t really afford it so he didn’t come and I said he was poorly to lower the cost. My and my sister were paying. There was me, her, her husband, her 4 year old and our Dad. I picked them all up and didn’t drink so that I could drop them off after, all other adults drank, they had 2 bottles of wine between them and 4 beers. The 4 year old had an adults steak costing £22 (and wasted 2/3- just pointing out so you know they didn’t have a cheap kids meal) the others all offered from specials between £19–27 and my sister and her husband had starters. I had an £11 pizza and a sprite.
At the end my sister messaged me saying I’ve been and paid our share if you want to go pay the rest (so Dad wouldn’t try pay). When I got there I was told the amount and said to the waitress “my sister has already paid some” with it being so expensive and she corrected me saying yes this is what’s left. She had paid half of the bill exactly, aibu to ask her to pay a little extra? She knows I’m broke and probably already worked out why DP didn’t really come. I expected they would divide the bill by 5 for the per person cost and me pay for 1.5 people and not 2.5! The amount it cost me I might as well have taken DP.