Getting frustrated with everything

I dislike the mother of my step daughter. I have been in the babies life since she was born. I have clothes her and made sure she has everything you need. I was there when the mother tried to kill her self and comforted her. I was the one who took her to the hospital when she has RSV. I have been made to look like a monster who wants full custody and I won’t lie, I do. Her mother has absolutely no job, no car, she lives off food stamps and wants my husbands child support to get section 8 which is totally fine I’m all for him taking care of his daughter. He signed the birth certificate of her oldest because they were together and now they aren’t obviously. He no longer wants to be on the birth certificate because she’s with holding his daughter from him. She has told us she wants us to take her and now she’s changing her mind and bashing me all over social media. She’s threatened to fight me and all this. She says I’m not wanted and I messed everything up. My

Husband says don’t pay any mind but she made a joke out of my brother passing away from an over dose the day after it took place. She said I’m no good for her when I worship the ground this little girl walks on. I get her even when he’s not home just to take her out and let her enjoy the day. I give her money and stuff. But she bashed me. Am I wrong for wanting full custody?