You’re not strange. I change my volume multiple times a day, too. If I’m in my car driving, I turn it down so the road noise is quieter. Sure, I can just leave it alone and get used to the road noise just the same, but I have a volume button and it’s one or two clicks, so why not?
If I’m at a concert, in between performances when people clap and yell out, I turn my volume down because I don’t care to endure that loudness. Then when a new performance starts, I turn my volume back up to default again.
If I’m at home and my wife runs the blender or dishwasher, I turn the volume down if I don’t need to have a conversation with her while this is going on.
If I’m at a restaurant and I talk with my wife, I leave my aids volume alone. But if I’m eating alone in a cafeteria at work, I’d turn my volume down so I don’t have to hear all the ruckus going on.
Some people like to set it and forget it, some people like to tinker with things. I’m just of the later type. There’s nothing wrong with either type.
To the OP, unlike your sister, I don’t turn my volume down all the times permanently, though. I turn my volume back up to default again once I change to a new environment that doesn’t cause enough bother for me to have to turn it down.