You sound like a great mum. I too have a two year old little girl who is not the clearest speaker even though she is smart and suprises me about how much she knows, she gives it a go and is also going through potty training as we speak. Maybe you could try and read to her on the potty or the "big toilet" if that's what she prefers (some days my daughter will only go on the big toilet). We have a 'thing' where we call out charge and she gallops like a horse to the potty or she starts differnet movements like hopping and I have to follow. We play games have some toys handy and talk to her about what is going on. I even bought her a cheap small doll which came with its own potty to help her get the jist of things. I am no expert but don't rush it, it happens in time, the more time you spend sitting with them the better they feel about going. And if it happens by accident when she is sitting there praise her by clapping, cheering, dancing, treats, kisses or whatever it is to help her realise, hey I this is alright.
As with the talking, I know every child is different and will develop in there own time. With my daughter she could mimic every animal noise there is instead of saying what they are or could show you what they do eg roos hopping, it's a learning thing and you don't realise what they pick up. My nephew was the youngest and has two older sisters, who used to still treat him like a baby and spoke for him, so he didn't need to speak and he didn't need to find his independence because everything was done for him. The girls mothered him, and it was only change of routine by taking the bottle from him and substituting a special cup he picked out and having it half and hour before bed. They got him to throw the bottle and dummy in the bin so it was no more and went with it. A few tears and tantrums some nights but all went pretty well and was soon forgotten. Also getting him into a playgroup and to play with other kids his age that he started speaking and picking up words and turned into a little man who didn't need his bottle or dummy for bed. Instead of the family reading to your daughter they could ask her what certain things in the book were or ask her questions so that she would have to answer, it will finally work it just takes time and patience.
Good Luck and keep me updated on how it is all going.