Why does she do this to me?

My sister often vents to me about her depression, having anxiety and how she feels like people dump all their problems on to her and she listens but she feels like no one ever has a solution for her although I give her plenty of advice. She literally comes to me asking for advice or tells me that I’m a “Good listener and problem solver.” She will send me messages that will weigh heavy on me because of how in-depth she gets about describing what she deals with on the inside. My point is the way she says she feels is exactly how I feel. The difference is I actually listen to her when she wants to get things off of her chest. When she mentions going to therapy and things like that I put myself in her shoes but when I even attempt to do the same she talks over me with her problems. She makes it about her again and if she does listen I can tell she doesn’t feel like my problems are as big as hers just from how she responses. It’s always generic responses”You’ll be okay. You’ll be fine. Now back to me and my damaging problems that are much worse than yours. You have no real problems like I do.”

Why does she do this to me?
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