BG
Tallgirlfriend and I are going on a weekend holiday to celebrate our anniversary. We're taking a flight from Mycity to my Homecity, and from there we'll fly to our destination. However, on the way back there won't be a flight from Homecity to Mycity for three hours. We decided to catch a train to the coach station and take the coach back to Mycity. We'd only save an hour's travelling time but we'd also save three hours hanging around the airport

My sister who lives in Homecity has been and will be frequently visiting Mycity over the next few months because she is attending some courses not available in Homecity. My sister hates travelling alone.
End BG
So Tallgirlfriend and I are very excited for our anniversary trip and much gushing of the details of our getaway has been done by both of us. I was discussing aspects of the trip with my Dad after going over our itinerary with him. Dad was kind enough to offer to take us to the airport (at a ridiculously early time Friday morning) and pick us up from the coach station when we were back in Mycity.
My mother entered the conversation and picked up on the date of our return. This will apparently coincide with my sister catching the coach to Mycity to spend the week with us while she attends her course. Here's how that conversation went:
Me (to Dad): "So we'll catch a plane back on the ??th and then get a coach from Homecity to here."
Mum: "The ??th? that's when S will be coming up. She can catch the coach with you!

"
Me:

"Doesn't she usually come up on a Tuesday? The ??th is a Sunday."
Mum: "Oh, that's alright. Since she hates travelling alone she can just come a couple days earlier."
Me: "I would prefer if she didn't."
Mum: "Why? You guys can all travel together! It'll be great, Tallgirlfriend and S can finally bond properly."
Note: S hates Tallgirlfriend. S doesn't look at Tallgirlfriend without a sneer, and doesn't speak without an insult.
The last time I made a trip to Homecity, S did tag along for the return trip and it was a nightmare. S did not have enough change for the train ticket so I bought her train ticket. While waiting for the coach I bought myself lunch, turns out S had no money at all. I bought S lunch to stop her yelling at me in public. S needed a bottle of water. S needed snacks for the trip. My every attempt at no was met with a half yelled "But whyyyy I'm your siiiister, I'm huuuuungry I have no moooooney!" in as petulant a voice as she could muster. I hated it but when she threatens to start screaming and crying she actually means it. Did I mention S is 18 months older than me? So I caved rather than have her cry, nay, shriek all the way home. I hope that puts travelling with S in perspective.
To put the holiday in perspective, Tallgirlfriend booked our dinner reservations for our anniversary dinner
six months ago. The restaurant is very posh, very in demand and the head chef is Tallgirlfriend's idol. And that's one activity on one day of the three day trip. Given the time and effort we have invested I am very protective of this trip. We have planned it to the last detail and, given the company, it will be amazing. I literally would be only slightly more excited if I was going to Disneyland.
Me: "Mum, we'll be on the way home from our holiday celebrating our
anniversary. I do not want to have to travel with S."
Dad: "We have booked S's coach ticket already for Tuesday as well."
Mum: "We can get it changed! It's two weeks away! I don't get why you're being so selfish Tallone, she's your sister and you know she hates travelling alone! Why can't you just be nice for once?!"
Me: "This is an important occasion and I do not want to end it on a bad note because I have to spend five hours on a coach with S. S and I do not get along. S and Tallgirlfriend do not get along. Tallgirlfriend and I will be travelling alone."
Mum: "I'm not discussing this any more. S is travelling with you and that's final. Tell me what time is your coach leaving."
Me: "No, I won't. I know you would like S to travel with us but I'm afraid that won't be possible."
And I rode off into the sunset! I'm know going to cop PA and probably regular aggressive flak for this for the next couple months but the choice was clear. Leisurely trip home canoodling with my lady love or five hours of putting up with S's entitled, snarky behaviour at every turn? No contest.