Hi Albaba. Firstly, you are doing a fantastic job. We each have great kids that unfortunately have challenging circumstances, and you cannot underestimate how well you are doing.
We have some similarities to you and some differences. Take encouragement from your DD talking, that's fantastic. Our DD2 (2YO + 3months) doesn't yet but she's desperately trying. We too think our DD2 has excellent cognitive skills and understanding, but she is so frustrated at her severely limited oral communication. Her non-verbal communication (facial expression, pointing, grunts/shouts) is excellent though.
At about 20 months our DD2 was just pulling up to stand, and doing some furniture cruising. It started off like yours, slowly and for short periods, but DD2 gradually built it up over time (with some help of strategically placed chocolate buttons on the sofa, just out of reach, to encourage and reward movement!). Now 6 months on, and she's almost independent walking (can slowly walk across living room but can't run, and can't sustain it for very long). So she can't run with the other kids in nursery, but she can hold hands and walk between play areas, and so joins in.
Her big sis is in Y1, and all the playground mums know about DD2's diagnosis and they are truly lovely and supportive. They celebrate with us any little success DD2 has. Being open with people really works for us, and I'm by no means extrovert. I think it would add to my stress if I had to work at keeping a 'secret' along with dealing with everything else. But I appreciate we're all different so you have to do what works for you. I have found that people don't judge us, they are supportive.
Occupational Therapy is worthwhile if you can get a referral from your physio or pead. They will help make environments accessible but there is usually a waiting list. I have a small kids chair (from ikea) that I manoeuvre around while DD2 is playing, so if she goes towards the play kitchen, I'll place the chair behind her there and she can sit while she 'cooks' etc. Has your physio mentioned a Kaye Walker to help your DD's mobility? If she's pulling to stand and cruising the furniture, she may be almost ready for a walker?
Please don't feel alone. There are a lot of us out there with youngsters struggling to walk, and there are some really lovely and helpful people on this thread. Stay with us and let us know how you are getting on. 