Why doesn't my pup like me?

I got a Maltichon about a month ago. At first she loved me. If i went to the kitchen, she would follow me, if I would go to my room she would follow me. If I sat down on the couch she would sit on my lap and rest. If I called her name she would listen and walk over to me, but recently my Brother's girlfriend... show more I got a Maltichon about a month ago. At first she loved me. If i went to the kitchen, she would follow me, if I would go to my room she would follow me. If I sat down on the couch she would sit on my lap and rest. If I called her name she would listen and walk over to me, but recently my Brother's girlfriend moved in and she has a yorkie. My pup loved playing with her yorkie and I was happy for her because she finally had a friend. After a while, my pup would stop listening to me. If I called her for her to eat, she wouldn't even look at me and just leave the room, and she would just eat from bowl from the yorkie (even if it was the same type of food). If I take her to the park, she would rather play with strangers than with me. I even potty trained her and taught her to sit and now she wouldnt listen and just does her business all over the living room (even if there is a pad). She would only listen to my brother's girlfriend.
Sometimes when I try to play with her she would end up trying to bite me. I rarely interact with her because she is always with the yorkie or with my brother and his girlfriend. Idk, she acts like she really really dislikes me. I also have other dogs but I give them the equal amount of attention.

Did I do something wrong? Did I not give her enough attention? What can I do? Because honestly this feeling kind of sucks....
Update: Edit: Okay, I know that the Matlichon is not a real breed. i never claimed it to be a breed. As I am reading a lot of the answers, all of you are saying that pads are bad, and I'm sorry for that, didn't know that, but I do take her outside. And to tell all of you this, the pup came from an abusive owner.... show more Edit: Okay, I know that the Matlichon is not a real breed. i never claimed it to be a breed. As I am reading a lot of the answers, all of you are saying that pads are bad, and I'm sorry for that, didn't know that, but I do take her outside.

And to tell all of you this, the pup came from an abusive owner. I felt bad for her and I took her in. (I knew this because of a friend of mine). I do not hit her because it's just straight up wrong.
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