Ant dream,
My mil also gives tons and tons of excuses for her actions. It was only after my boy was born that I realised my hb is so much like her. They always think they are right and i must follow their way but they never admit they had done something wrong.
For me, I don't think it helps if I change my perspective by thinking mil and sil are trying to help. Certain things that they had done were so obvious that they wanted my boy to be bonded closer to the unmarried sil than me. And they also wanted to make me invisible when we were at mil's house. I know they would succeed if nothing is done to stop them. So I change my perspective from passive to active.
I used to think it is fine, let them do what they want, I can spend other time with my baby. But again and again, I was disappointed. I realised they would never allowed me to spend more time with my boy. I began to be active in mil's house. I approach him, talk and play with him. As I began to be more active, they knew their 小动作 not going to work. So mil started to say very loudly that it is very tiring to look after baby at night, they can help to take care when we are at her house. But I ignore her comment and continued to talk and play with my son.
Tired as you may, but never give up your rights. I am sure one day, you will find a way out.
I never quarrel or argue with my mil. I know that would set the whole family against me and making it difficult for me to go near my boy. So I use the excuses or tactics they had used on me, to prevent their actions. Mil and the unmarried sil always tell my boy what ah ma or er gu can do or had done for him or say he never greet them. To me, it is a mental torture to repeatedly hear the ah ma or ergu every few seconds. So every ah ma or ergu I heard, I counter match with a mama for my boy. Not sure if it is a mental torture for my boy too but it did stop them from doing so frequently.
I know I sound like I don't want my boy to bond with my in laws. But if they had not done it to me, I would not have done so at all. I am not a fighter or aggressive but it doesn't mean I can be bullied.
Sorry for the long post again. I just hope my little success will encourage you to find a solution to your problem.