Is it normal that me and my best friend slag off our other best friend

I have two best friends, but for privacy lets just call them W and R. We started high school just 3 months ago and are fairly popular. But in the past few weeks I noticed that W started talking about her life as if it was shit-ALL the time. My family is in debt,my parents are always arguing. my mums always on her phone talking about care homes for my grandma,my grandmas practically dying and the girls in my class aren't friendly. Her class is perfect and she's always complaining about it. R came to mine for a sleepover recently and i mentioned it to her.She agreed and said she's been thinking about it for months. Eveything's about W. So we were really upset.Her brother and mum are constantly arguing and she has had a HUGE boy problem for THREE years. We never talk about our problems to W because whenever we want to be sad, or talk about a funny thing that happened in class, she always interruppts and starts a new story or whenever we mention someone she always talks about how much she LOVES that person, like she's trying to convince us that she knows EVERYONE.I barely mention any of my problems and neither does R. So we have a plan. If W interrupts either of us then the other person(me or R) stops W and lets the other person finish.WE think it's working.
I feel really guilty and not sure if i should talk to W about the way she's been acting.Please help/give advice. Thanks xx