<human>: Can you provide a brief overview of the text?

I'm 19 (f) and he's 20 (m), and we've been together close to four years. 

I really like his mother, and she really likes me, but her and bf have a really strange, unstable relationship. Even though she treats me great, and I know that she loves him, sometimes she just does the craziest things to him, and it irks me!!

For example, he has been taking a break from college after a bout with depression caused him to drop out about a year and a half ago. Things have not gone well for him, but I finally talked him into giving it another go. He asked hid mother, (who brings in the primary income, holds all the tax documents, is essentially the law) to do his FAFSA. She replied that she wouldn't help him, he was on his own, even though two days earlier, she made some snarky comments about him not being in school.

She is also remarried, and he doesn't get along with his step dad, and on their most recent family vacation, left him homeless for a week! I get along with her quite well, but their relationship is AWFUL, and the random crap she does out of spite really upsets me. So here's the question finally: How should I act? I feel two faced sucking up to her, but I love her, and I was taught to respect my elders. But I also catch myself bad-mouthing her when they get into it.
<bot>: Sorry for the wall of text. Authoritarian mother treats me better than her own son. How should I behave without being a hypocrite?