Lisa was mentioned briefly last week. When Louise showed up at the door with bags, she told Ben that she fell out with her mother and moved out.
If it was mentioned then i clearly missed it, but i don't remember Lisa being referenced in knowing her daughter was in hospital and seeing Phil. I hope Lisa does make a shock visit, because I can't see Lisa being a fan of her daughter wanting to know Phil, after spending most of Louise's life keeping her away from him. It wouldn't be true to the character of Lisa to be referenced that she isn't bothered about it. Because she would be.