I am glad you are going to ask Emma what's going on. But you willl just nod and smile.
It is being a poor friend to be like this - and a poor human for yourself too. You allow no challenge to yourself or others, which means you opt out of inviting others to grow. You have allowed your family trauma to keep you stuck - you see the world as only either anger and confrontation OR appeasement and making yourself small.
Challenge and assertiveness can be done with love. Kind clarity is a key part of good relationships.
OP on some level you're not happy living like this, are you? That's why this is bothering you and why you posted.
You are keeping yourself small and surrounding yourself with people who also have no interest in growing. Excluding and bullying are about fear and control from the bully. You are all operating from a place of fear.
I’ve no interest in politics anyway and I just don’t challenge her because life is easier that way, not just with Emma but with other friends and family
Being uninterested in politics is another fear based stance, politics is the conversation about how our behaviour to one another should best be regulated. You can't even handle it in 121 relationships, no wonder your brain is telling you that it's "boring" at larger levels.
But the world is out there. People need rights and protections. People like Anna, Emma, and you, are part of society. You have to stand up for good behaviour - like not perpetuating rape culture by allowing misogyny for example. Like not allowing people who have less social status (eg the single mum vs the shiny new partner) to be left out. It is literally the same process as excluding and minoritising disabled groups, ethnic groups, women, and so on.
First they come for the Annas, then they come for you.
You might not be interested in politics but you are doing politics. You don't get to sit this out.