I think your problem is in the rings and it is wise to go to the mi-milage / thicker oil. I have an idea your documentation and recording is exact and hopefully you will cut your consumption in half. Still not great, but maybe She can go for 1 oil change and not have to add any?
The strange thing still is where is the oil going? I'd like to follow you for 1 hour and check MY windshield. lol.