So I struggle with anxiety and depression, and my sister struggles with depression and likely bpd. We fight all the time and it usually ends with her using her mental illness as an excuse to neglect/be mean to others and completely neglect her responsibilities. I can’t get her to empty the litter box or take her dishes out of the living room without a huge fight that ends in her screaming and saying it’s too hard to do anything because she’s so depressed it’s hard to even get out of bed. She will say these things and then go do other things like do her makeup and go on a date, make food, paint, etc. Personally, I struggle to get out of bed every morning and get ANYTHING done, and it takes a lot out of me to accomplish basic things. But I still do what I tell others I will do because I actively try to have integrity. 

Is she just being a defensive, immature teenager or should I take her defense seriously? I imagine this is how many parents feel. I want to have a good relationship with her.