Last time they visited me here, they didn't stay at my house because I was doing renovations. We made arrangements one time to eat dinner at their own hotel restaurant, reservations at 7 p.m. 7:30 arrives... they're not down. I call their room.. my mom says they'll be running a little late. I eventually ordered, ate my food alone still waiting for them. When they finally sat down, it was 8:30, and my dad apparently had "problems with the shower." Completely casual restaurant... they don't care if you have no shirt on. I still am a bit mad about this...
Problems with the shower? Is that what they're calling it these days?
I am a reformed late person! I used to be late to everything- work, lunches with friends, church, you name it. Not super late, but anywhere from 5 to 15 minutes. I hated it and I know it annoyed the people waiting for me. It's just plain rude. Plus I always was panicked and had a sick feeling in my stomach as I was racing to the event. I was just a horrendous time manager.
So I decided to change. Two years ago I made a conscious effort to never, ever be late again and I have to say I am really doing a fantastic job. I start getting ready way earlier than I think I need to, and leave earlier than I think I need to. I now show up early to things which never happened before.
So we are capable of change!
Yeah, I'm working on that myself. It's neat to slowly change. DH and I have left things so late that we've been late to two of our OWN parties.

Since many of our friends are latecomers as well, as far as we know that hasn't messed anything up, but then again, there was a whole group of people that we expected to come to the first one but didn't show, didn't call, and never mentioned it the next week. So it's possible they came on time while we were out getting ice, and the whole situation was just too embarrassing for everyone.
I read an article once that called some people "time optimists" - they under-estimate how long it takes to get things done, and so they end up running late. My grandmother was one (and it's hard to be mad at a sweet old lady) so we always just told her an earlier time, so she would actually arrive when we wanted her to.
I know your friend is the one being rude, but being angry about it affects you way more than it does her, so the simple solution (even if not technically "fair") is to just fudge the schedule. If you really need her there by 9:00, tell her you want to leave around 8:00. - It certainly won't hurt the dogs to be early if she magically makes it "on time".
I absolutely LOVE that, and feel that it's a perfect description. Time Optimist! Yes. Now that I've started to change, started to be really realistic about how long it takes to be ready, get out the door, etc etc, I've noticed that DH is a TO person (see, it already has an abbreviation!). We'll plan to go somewhere. He calculates how much time it takes to get from the street, or even the highway, to the destination. He doesn't take anything else into account. Not realistic time to get ready (he continues to calculate ONLY for himself, and he takes way longer than me to get ready most of the time, even if I'm putting on makeup), not time to get shoes on and out the door, wait for the elevator, chat with neighbors (we rent in a condo building that's mainly for retired people, and people here are chatting and NEVER in a hurry), get the car out of the garage, get out onto the street, then to the highway or the street across town, and then no time for parking and walking right to where we're supposed to be.
I've started having to break it down, and that's made all the difference. So if DS has gymnastics at 4, and I'm going to work out for an hour ahead of time...the old me would probably be leaving for the gym at 3. Already late! So now I go backwards. On the mat at 4. 5 minutes to get from workout room back to gymnastics room. 65 minutes (one hour plus cooldown), plus time to get onto the machine with a towel and get water and Kindle situated. Walking from car to gym and sign into gym. Parking. Get to gym from driveway. Get from apartment to car. Prep time in the house.
When I break it down, I do well. And what amazes me is that, I think, many people just do all that in their head *naturally*. For me, it's a huge effort. But for others it's just what you do.
About your second paragraph, though...honestly, if people were giving me extra time because they knew I'd be late, that wouldn't help me at all. I would have rather known the absolute time, and I would take the consequences if I were still late.
I do have to say, for all those who absolutely hate latecomers, feel it's a slap in the face, etc etc...I know for certain that all the things you're attributing to the latecomer isn't true, at least for me. You guys think it's ego, but it's not. It's just absolute failure to understand WHY we're late. It diminishes the ego, it makes us feel bad, to be late all the time. It's awful, not a good feeling. Think it feels GOOD to get everywhere looking like junk, because you misjudged the time and couldn't do your makeup? Or you did your makeup but then had to run in the heat? Or in the rain because you ran out without an umbrella, or didn't feel you could take the time to open the umbrella? To always be windblown, sweaty, red-faced, because you were rushing so fast? It's NOT a good feeling.
I'm sure there are some who just WANT to make people wait. But I know I'm not one of those people. And I know I'm not alone.