Wow, that sounds like my grandmother's stepmother; she was a second cousin and only 12 years older than my grandmother. My grandmother's favorite, older brother was only 3 years younger than his stepmother so he kind of like left home? She was 18 when my great grandfather married her. My grandmother's mother died when she was one so she was a little hellion by the time she was six and finally ran away (my aunt says eloped) from North Carolina to Idaho when she was about 18, the older brother was there in Idaho. She went to the University of Idaho and met my grandfather, etc.

My husband's ex- sounds a little like her too. My husband's ex- does a whole lot of complaining. Asking her how she is is often not a good idea :-)

I would just try to "make friends" with your stepmother, not think of her as a "mother" figure but more as a wayward school acquaintance? Not everyone we meet is to our liking. She'll be your father's wife, not yours :-) Just try to stay vague about your plans and problems so she doesn't offer too much advice, stay polite to her, etc. Bring a school book or novel or something with you when you go to their house, not anything very "personal". I'd explore the area a little, see if you can find any other teens to hang with when you're there? Do you know that part of town/area very well?