I started behaving like this, always ordering my tins and jars in the cupboard by what they were, their use by dates, they all had to be perfectly placed and in line, and I stressed if I had the wrong number of something so things didn't fit.
I have to have pillowcases the right way round. Duvet covers have to be pointing the right direction. I absolutely hate the open ends of pillowcases but velcro would make the edges too hard for me.
My books were lined up by size. My clothes were folded and arranged by type, colour and whether they were more goth, or more mainstream.
I also put food into labelled containers. This eventually extended to me putting ^everything^ into containers with labels.
I also put out most of my belongings and could fit everything of mine into a small car.
These are things I did because I had a massive breakdown which resulted in a lot of psychiatric intervention.
You don't necessarily see the change in actual personality. In my case there was, apparently. Memories from that time are still patchy with me. But I have a lot of OCD traits and it's linked to my mental health. My mannerisms are more noticeable when I'm not well.
I think it's good that you're able to notice these things and feel concern for your friend. You never truly know what's going on inside a person's head and anything could be going on behind closed doors, or at work, or wherever.
I just wanted to post to say that I think voicing your worries over your observations was a positive thing.