My mom

I’m not sure if this is the right subhead to post this on, but my relationship with my mom is under stress so I figured this was close enough. The last couple days, my mom’s been saying she’ll do things with me or telling me she’ll help me find something I’ve been trying to find, but she just doesn’t. Instead, she’s been playing video games with my sister. Driving practice, shopping for things I needed, helping me find something she said I could have. All these things are things she neglected to play video games with my sister. I love that game too, but she only plays with my sister since “she’s more fun to play against.” Once she decides to play with me, she’s too tired and will fall asleep midway through our game. I asked her today why she only plays with my sister and only asks my sister to play and she immediately got defensive, saying she hadn’t played with my sister in the last hour, but she had asked my sister to play and played multiple rounds with her before sending us away so she could play by herself. I brought up the last couple days where she’s only asked my sister, and she told me not to be jealous of her and that she knows my sister will always play with her, but I’m too grumpy to play. I feel as though this isn’t true and just her trying to defend herself. Am I looking too deep into it?