How do you expect people to love you when you don't give them a chance to bond with you?
I know everything is hopeless when you're fifteen and depressed, but here's a few things I learned as a stepkid whose stepparent entered my life when I was 14:
It is absolutely possible for a step-parent to love you.
It is possible for them to love you even if you were a dick to them when you first met them. Even if you were a dick to them and ignored them for several months after they first entered your life.
Love is a two-way street. Your step-parent cannot bond with you if you don't give them a chance to get to know you. You have to spend time with them, talk to them, communicate your needs to them.
Shutting yourself away from people, ignoring them, and wallowing in depression will only make your life worse. Depression is the disease that tricks people into becoming alone so it can hurt them even more.
My suggestion would be to spend time with your stepmom and her goddaughter. Do something age-appropriate for a two-year-old girl that the three of you can do together, and use that opportunity to try and talk with your stepmom.