I don’t believe you should be telling 3 and 1 year olds that mom and dad have problems. They are too young for this information. It seems like both you and your partner involve children into your conflicts, it’s not recommended. Their extreme attachments to one parent and then switching to another is them seeking immediate comfort and trying to calm their anxiety.

Your daughter behaves like many children who grow up in volatile and abusive households. I don’t think you can get into her head and make her change her mind or behavior, kids learn by observing, their behavior is a product of their environment, currently their environment is unhealthy. If you want healthier behavior, kids need to be in a healthier environment.

They are too young to learn by what you are telling them. It doesn’t work that way.

Could you see a therapist yourself? Soon your older daughter will need therapy as well. Your kids are being traumatized