To those who know a lot about mental health: what could this be?

Someone I'm very close to has several interesting and rather bothersome characteristics, that I suspect may be indicative of perhaps mild autism. I will list the behaviors from least unusual to most.

She tends to get very interested in certain subjects, often writing lists. This habit of getting very deeply interested in a topic has improved with age, but she still writes lists sometimes. She enjoys organizing and has written labels all over her room. She making schedules and simply organizing in general.

This person, when walking with groups of people always walks off ahead or wanders off, and seems unable to how to adjust herself to group behaviors. Another group rule she seems to violate is her tendency to just leave, dinner, events, etc.

When I walk side by side with this person, she will walk faster, so that she is a foot or so ahead of me. It's kind of an understood social norm that when you walk with a person you are side by side.

This person pacing excessively. She simply cannot have a day where she doesn't do it.

When she paces she is very quick. She looks down, usually lost in thought while doing it, often smiling at the ground. She is so lost in her world it has happened that she bumps into objects, or even walks right into people! Once, she walked right into a car while she was looking down and lost in thought, looked up confused, and then simply went around the car, seemingly unaware of how bizarre it was that she had just walked into a damn car.