My step daughter resents that I "Made her Mom a lesbian"
I am in a long term relationship with a mother of three(f16, f10, m8).
She and I have been friends for over 12 years, since before her two youngest kids were born, but did not start seeing each other until she and her husband (the father of her two youngest) had been separated for nearly four years.
Despite this, I am not his favorite person and I feel that he has imparted this onto my partners middle child (f10).
My partner and her kids have been living with me for over 3 years now and each day gets just a little bit worse.
I love her and her kids and for the most part everything is great, the eldest and youngest love me and are caring and respectful ( well as much as a teenage girl can be for the most part) and on the whole there are very few dramas when it comes to them.
On the other hand the middle child is really starting to make it impossible. She is disrespectful, rude, nasty and selfish, spoilt (mostly by her grandparents), manipulative, ungrateful and resents me for "taking her mother away from her dad and making her a lesbian".
Her behavior while always a little on the cheeky side has severely deteriorated since she and her brother returned from spending Christmas with their father, and every day gets just a little bit worse.
Recently my partner had surgery so most of the parenting has fallen to me which I believe is also a catalyst for the increase in resentment. As i am needing to be much more hands on and with her, were as in the past i tender to leave her to her mother because she has always been a little emotional.
I constantly hear, "your not my mother", but i cant help but feel like i deserve a bit of respect since i am at the moment the primary care giver including cooking and cleaning, washing, taxi as well as the bread winner which includes sending their father money when he has them, it is my house we live in, and for nearly 4 years i have cared for them, looked after then, ensured that they have everything they need, not to mention when they were smaller and their mother and i were just friends.
It is also causing problems with the other two as they start to resent her for her treatment of me, and i don't want to be the cause of them fighting.
I honestly don't know what the do. I want this to work and i don't want to give up loose the love of my life and let the other two down.
Please can someone give me some advice?