To Guest with extended family issues, hi.
I'd like to express a different take on this, leaning closer to bunny's comments and asking some questions which I don't need you to answer, it's just food for thought.
You said you rang her.
Who bought dad into the conversation? If it was you then it's possible she was reacting, feeling like the ham in the sandwich, and maybe was threatened by feeling like you expect her to take your side against dad's. You say she's doing things to try to control his contact with her, things which she shares with you. By doing these things, like not answering the phone, it seems she may feel she's setting some boundaries.
If she bought dad up first, and then criticised you for your feelings and attitudes and comments, is it possible to discuss with her the option of you 2 sisters having contact and a relationship where dad is excluded from the conversations. Setting some mutually supportive boundaries which include placing no expectation on each to relate to dad in each other's way. Can you ssk her to not bring dad up when you ring her, because it just drives a wedge between the 2 of you and causes you grief. Can you ask her if she thinks it's possible that the 2 of you can relate separately as sisters and have a relationship and conversations where you mutually agree not to talk about dad and develop your own relationship.
I've done this type of thing with my family members who used to often bring up my estranged parent. Whenever it happened it would bring memories back that I wanted to leave behind and we would sometimes end up having unpleasant disagreements which left me feeling even more isolated and misunderstood. But since requesting, for my peace of mind's sake, for them not to bring the parent up to me, I have on the whole received good cooperation with understanding. The benefits have been that we have so much more to talk about that's interesting and enjoyable and don't get into the dramas we used because of mixed up feelings of loyalty.
As far as your little boy goes and how bad you must feel for snapping at him, you're human and sounds to me like you're sorting through a lot. I'm glad you recognised it was inappropriate and found somewhere more appropriate to vent. That's what happens sometimes, isn't it, when we're confused by what hurts us. And feeling misunderstood. It's so important to look within and get an understanding of our weaknesses inherited from unhealthy parenting. This way we can stop passing on our own particular family's illness to the next generation. We can be different and so much healthier than how are parents were. Wishing you and your son happiness.
Guest.