Is it normal for friends to change the subject to themselves every time you talk about yourself?

I have this close friend, who I’ve known for several years. She used to be a sort of attention seeker but over the years she’s grown out of it. Any time I mention something going on in my life - good or bad, she somehow finds a way to talk about her life and how she’s having a similar experience or similar stress. It’s annoying honestly, it feels like i can never vent to her without her comparing her situation to mine or overshadowing mine. But when she’s talking about her life, I always make sure to keep the conversation focused on her only. How do I go about mentioning this to her without sounding rude?