No one ever said that parenting was easy … unless they weren’t parents. The fact is that you are her advocate until she can do this her self. Since you took on the responsibility of being a single mum, you are her primary advocate. The hell with it not being easy, you do it. It is obvious that you are the one to advocate, her dad doesn’t notice anything is going on!
It won’t get easier, as she gets older. The issues just get more complex. I am a very non-confrontational person but do not hurt my children in any way or you will have a grizzly to deal with.
You know what you are doing is the right thing despite other people’s opinions, so carry on!