(((Siempre nada)))
I disagree with your sister's perspective. You are different people, with different outlooks on life and different interests. That's okay!
I did make a couple of friends in college, but I was older when I went to college. I was married ~ and I didn't put any effort (or pressure on myself) into making friends. As I've gotten older, my perspective on friendships has changed quite a bit. It's pretty normal for friendships to come and go as we change throughout life. Different experiences connect us to those who can relate to what we're going through.
That's my perspective... try not to feel hopeless for the future. I hope that you're seeing a T, to help you work through your depression. Are you sure that you're majoring in the right area for you? One that actually captures your interest and devotion? That helps with depression too ~ if we're involved in some thing or things cognitively and emotionally. Best wishes!!