why is it so hard for this Leo to get along with her Gemini sister?

Firstly, I apologize to all the Geminis, as I am pretty sure this has little to do with her sign but I am trying to look at all angles here. My sister is 14 years older than I am and impossible. She has narcissistic tendencies (after studying my own sign I swear she seems way more Leo than I do) starts arguments over literally everything. I am very introverted and she always wants to talk, about our feelings, about our relationship etc but when we talk she does all the talking! I can't get in a word and if I say anything "I misunderstood" and she says why can't you let me be right sometimes? as if right and wrong are somehow not finite. I don't believe in relativism. 2+2 is 4. if you say it is 5 obviously you are wrong. We aren't talking shades of gray here. I am not saying I am perfect or I always get things right but why would a person be wrong for a change on purpose, you get me? She is also Bipolar which adds a whole new angle to our relationship. She takes me for granted all the time. I have a hard time saying no and so I am always bending over backwards for her. When I do say no she always gets mad and personal. She is an expert at hitting below the belt and I always end up in tears and then she turns the tables and tries to make me seem like the crazy out of control one. Anyway just wondering if there are any issues here that stem from her sign and how I can learn more in order to keep the peace.

I have a gemini sister and she's nothing at all like this. We both have good communication skills and even up to this day we still keep in touch via text. She's also a whole lot like me quiet and keeps to herself tho she has a hand few selective friends. My relationship to my gemini sister I wanna say is a whole lot better than the rest of my siblings. I feel like a total stranger and out of place to the rest of them.

I would probably say look further into her full chart. It's more to do with just gemini sun alone.

Also like to address all Geminis is very well capable of hitting people below the belt even the quiet ones. You have to keep in mind gemini is the sign of the twins. You'll get the best of both worlds with us.