My 99 is exactly the same as yours. My situation is same as your. 我99 is very very 偏心細新抱 (not because she is pregnant but because 99 can control 細新抱).
So no matter what I have done to 99 (e.g. buy good stuff to her), she still treats me very badly & deliberately treats 細新抱 very very good in front of me all the times (e.g. I can only eat what 細新抱 not eat, everyone has red pocket money from 99 except me, 99 celebrates everyone's birthday except me etc.). So I was very very hate my 99. Because of that, I also feel very upset & this even affects my health (emotion affects physical body, always sick, not sleep well) for the past 4 years.
But now, I know I'm not living for 99 or 細新抱. I don't care what my 99 says anymore because I treat her as outsider (because she treats me as outsider first !). I don't always appear in their family gathering, I don't buy gifts to 99 anymore. Like the sisters say above, if she doesn't like you, even you buy her a gold, she will not be pleased !!! So I better concentrate my own life & my happiness.
When I married with C6, I wanted to have a happy family, so I was willing to treat 99 well. But what she has done on me made me very angry. Now, I only do a PASS 新抱, not DISTINCTION, because she doesn't deserve me to treat her any good now !!!