20 month old preemie... Sensory Integration???

My 20 month old preemie isn't walking yet due to very low tone on her left leg and hip so holding up her body weight is difficult....she's in PT and will do it for her therapist for up to 30 seconds at a time. The problem is she has a terrible fear of letting go and always needs something in front of her while standing or has to at least lean onto something or hold on one handed. She, too, doesn't want to bear weight onto her feet when you put her down, but lately has been doing OK with this when she has shoes on. She does well with a push toy though. She, too, doesn't know how to suck out of a straw (only tried once since I didn't know that kids should have that down by now) and really favors her left side; however, is a left handed eater. Her pediatrician recommended OT to come out and look at her and maybe get some sensory integration going for her fear of falling and getting her on a balance ball. What say you? Has anyone experienced this with their kids?