I am sorry that things aren’t easy but honestly when we have careers/jobs that involve caring for vulnerable population: mentally ill, developmentally delayed, young children, elderly etc, some difficult behaviors are to be expected. It doesn’t mean you should be ok with it but it’s not unusual.

Honestly having thicker skin and not taking it personally does help a lot. If working with this type of population is a challenge, then it might not be a job for you.

Do you have a formally established break? If yes, you could use that time for playing on your phone. If not you should request a break. I’d say you should have a short break every few 4-5 hours or at least I think so. I don’t think you should play on your phone at other times

I think her acting childish and having hard time making decisions is due to ASD, not her trying to be difficult

Things that you do for her are part of your job. I don’t think it’s you doing her favors. Not sure why you buying her gifts though. That’s so unnecessary