Why is my 13 month not crawling/ cruising/ walking?

i have a 13 month baby girl. she is well able to sit unaided and will sit and stay in same place, making no effort to move much at all. when i go to pull her up by her arms to a standing position she puts no weight under her feet at all,, when i go to stand her on the ground she just pushes her legs out to the side with no balance whatsoever r.. i have mentioned to gp who has referred her to a physio therapist andpediatriciann. he mentioned soft legs has anyone ever heard of this please