That was not an error of judgement at all, since you did not have the necessary information to judge the situation. I'm sure it was embarrassing for you, a foot-in-mouth moment, but you didn't really do anything wrong, let alone critically wrong.
And NT's do this same thing all the time, too, it's not especially an Aspie thing. Just today, a male friend of mine online was making joking comments about 300 pound men wanting sex with me, never knowing that my husband weighs a hefty 450 pounds. When I laughingly told him, he was horribly embarrassed and made a point of apologizing. Luckily I told him I found his foot-in-mouth moment hilarious rather than being offended in any way, since I knew he wouldn't have said it if he had had the pertinent information that he had no way of knowing. It isn't that common, after all, for husbands to weigh 450 pounds -- or for friends to die in horrible freak accidents. It's not like these are predictable events.
I'm sure your friend forgives you for the well-meaning joke, as she knows you had no idea anything serious was wrong. Just take a deep breath and brush it off and go on with life, knowing nobody really minds what happened except for you.