my emotional sister

I was having a conversation with my sister and she was saying how my parents make her feel small with the comments they make. I told her that its not them that make her feel small but her own thoughts about it. She engaged for a moment and said ‘well I was thinking that I’m not doing it right’. To which I replied and that’s what actually makes you feel small, your thought and not our parents. She became annoyed with this and said well that’s not how it is. People do things that are difficult or annoying and then I feel things. That’s just the way it is. She then left the conversation as she was busy.
My question is how can I help to explain to her that our thoughts create our feelings? She seems to shut down and enter defense mode when I explain the model to her. She appears to want to remain in emotional childhood. She is a very emotionally driven and reactive person so I would love to help her. She uses the excuse of having a one year old who does not always sleep well for her emotional volatility and lack of time to listen to anything involving deeper work on her part.