I had a similar case. At 1 year old when she started with me she could not get up by herself. She was crawling though. If I helped her to hang into something in the standing position and let go she would fall down. She showed some other delays in her development. She walked after 3 months and improved a lot. I think she was more motivated here than at home to move around to be able to get toys to play with. By 18 months she new some colours, was able to eat with with spoon, and was able to control herself very well like waiting for her turn all the time when she wanted something. She is now a very smart 4 years old... If the doctor says that she is healthy it could be that at home they have not let her do things that she is capable of because they do not want her to get frustrated.