What is probably true of her mother?

Choices:
A. She was unhappy in her marriage
B. She was happy but needed an extra relationship
C. She just liked having affairs
D. not enough information
She was unhappy in her marriage
Yes, after my mother died I found out from my supposed half-sister that my dad was not my birth father. She was 19 yrs older than me and had been living in Colorado since I was young. I was born and raised in N.J. I did not see her she did not come to see us. I was grown, married, had children and was living in FL. when she showed up at my door with her husband. I was shocked since we never heard from her and I did not know she even knew where I lived. She stayed all of about 20 minutes, just long enough to very unpleasantly state that “my father is NOT your father and I am NOT your sister!”
I always wondered why my mom hated me SO much, I found out that both my mom and “dad" were having affairs while married and both had children by someone else. I have never met my birth father (to my knowledge) only know his name, but understand that he was the father of my supposed half-brother (which would make him my only whole sibling out of seven siblings.)
Obviously my oldest “half-brother", who is 20 yrs older than me, is not actually related to me either.
I don't have for sure “proof" about my other siblings, but they all have strong resemblances to my “dad" and each other. Growing up people would comment about how much I looked like my mom but I also was told a lot that you would never know me and my other sisters were sisters, we used to laugh about it as kids because my sisters (all light haired/light skinned) and I (dark haired/deeper skin toned) were very different in appearance but we “knew" we were sisters.
I also found out that my apparently ONLY whole brother, approximately 9 yrs older than me, did not even know his real fathers name even though he knew our “dad“ was not his birth father.