Rarity's parents are… definitely something. They aren't home often so they've never really had the chance to get close to Sassy (or Petunia Paleo aka Sweetie's wife). They can both be forgetful and maybe even confuse the two.
Don't worry Cookie Crumbles has definitely mistaken Petunia for Sassy as well. Cookie asking Sweetie a few times "I thought your girlfriend was a unicorn?" and Sweetie just forcing a smile and replying "Nope my wife is an earth pony mom, you're thinking of Rarity's again." "Ah you're right, i'll get it right one day."
Hondo is one of those dads that just assumes things annddd is usually wrong half the time. A lot of his comments seem innocent to him but are taken awkwardly by Sassy. He IS a sports-man so it makes sense he'd tried to bond over sports! Right? Well this isn't the first time he's asked about sports considering her tall and skinny figure. Sassy has probably told him a few times that "No, I never was into sports.. I liked fashion and drama as a filly."
Luckily after an exhausting, physically draining day with them she gets to just come home to Rarity and snuggle and recharge. She might take the next day off to properly get back into the swing of things because it seems they literally drain her life-force every time. Rarity can't say much about, she knows her parents have always been like this and they travel more now than they did then. Do you know how often they would mistakenly ask Rarity when her next concert was? Or Sweetie's fashion show? It's honest, little mistakes! Every parent makes those sometimes! Right? Riighhtt!

Thank goodness Sassy sees them so rarely, she really did try to get close to them in the beginning! But she caught on pretty quickly that they have the poorest memories. Can't say their interaction with their grandkids is much better, I mean they remember their names! Sometimes- Well it's not their fault they have 4 grandkids! That's a lot! But they get the best presents when they come home to visit on holidays. So it's all good : D