I told my girlfriend I was surprised at how hot her sister is. Is that a bad thing to say?

I'm 24 and I've been dating this girl for a long time. She has a sister who's about 23. I mean they're both beautiful, her sister just a slightly different type. I'm so used to my gf by now, that I honestly didn't even pay attention to her sister's face or body when we met for the first time. That was maybe 5 years ago.<br><br>For real, it literally didn't even cross my mind. I was too busy with my own problems and going through a tough time. All that was on my mind was how to be a good impression and do my best to be nice, supportive, etc to my gf, and get along with her sister. I mean they're both different types, and I really didn't have a preference. Also, my gf was already hot looking and beautiful to me.<br><br>I wasn't even checking her sister out when we met. I didn't even think about how attractive she was until we met again, and she looked more different. In hindsight I realize it was probably because she was thinner and in better shape. She also had more confidence and was smiling more. I didn't realize it at the time, but looking back, she's a bit more outgoing too.<br><br>My gf would sometimes bring up her sister around me. But they're not very close, at least they weren't, but I think they're better now. Anyways, I would bring up things like "oh, I'm sure she does", "yeah, she's probably like that, she's a great person". I was just being my supportive boyfriend self, and she said something like "you don't know her well, how would you know?". And I replied with something like "because you're that kind of girl too". I don't remember exactly what we said, but then my gf asked me if I thought her sister was pretty. <br><br>I said something like "yeah, no, she's very good looking". She said "I'm not asking that, I'm asking do you think she's prettier than me?". And I replied with "yes, I think so". For that second I genuinely believed it. I mean, she kind of was, at that moment in time, but looking back now, I don't know, maybe it was the confidence. Anyways, my gf got upset and said something like "wow, I didn't think you were that kind of person". I was just trying to be my genuine self, but now I regret it. <br><br>She went on to say something like "you're my boyfriend, I would never ask you that about other girls". I know that now, and that's how I understand it. But I'm confused because I thought I was doing her a compliment. It's like I was saying "yeah, I'm a bit surprised your sister is that hot, but I'm glad you two are similar" I mean, isn't that a complement? To be compared to a beautiful woman? I mean I realize now that I made it about her sister instead of her. I just genuinely couldn't see myself with her sister, because that's not really my type, even if I was surprised by how hot she was when we met. I think my gf realized that, but that didn't matter. I fucked up.