AITA for telling my sister her husband stinks?

I’ll get straight to the point: My BIL does not like showering. My sister has casually mentioned in the past how he showers once every 4-5 days because “he doesn’t really get dirty.”

He has extremely strong BO and I don’t think I’ve ever been in a place with him where he did not stink. Even fresh out a shower, you can still smell very strong hints of sweat and…other types of smells when you’re standing near him. People have brought this up with her in the past, and every single time she just shuts them down and says that they’re looking for excuses to hide that they do not like him.

One of our mutual friends is getting married in 3 weeks and it’s about 9 hours away from where my sister’s family and I currently live (we do not live together, but we’re about 15 minutes away from one another).

My sisters informs me a few days ago that she will be riding with me to the wedding because their car is having some engine issues. None of this was discussed, she just informed me like she was relaying a message.

I cannot explain to any of you how much I shiver at the slight thought of being in the same car with her husband for 9 whole hours. He does not like sitting in the back and will most likely ride shotgun. To avoid this, I offered to lend my boyfriend’s car to my sister, as he is out of state for the next few months and will not be using his car. She repeatedly said no, no matter how many times I insisted.

So, I decided that the best choice for me is to just book a flight to the location and rent a car from the airport when I land. I have some points I can use to get a discount so it all works out.

I tell my sister that I’ll be taking a flight instead of driving, and I told her that she can feel free to use either my car or my boyfriend’s car if she’d like to drive there. At this point, I haven’t booked my flight yet, because I wanted to inform her before I went ahead.

She fully blew up on me and demands that I cancel my flight (because she thinks I already booked it) and says that we will be going forward with her plan instead. Continuous arguments led to the truth, where she lets it slip that their car is fine, they just didn’t feel like driving or wasting money on gas and tolls and were just looking forward to a relaxing drive across the country.

I was tired of beating around the bush, so I just told her the truth, in a very polite way because at the end of the day, she is my sister and the person I’m talking about is her husband, so there’s no point in being harsh.

She gets beyond upset and just blasts me with at least 50 texts about how I’m an A-hole. I feel bad about this but I’m truly conflicted.

Was I the Asshole?