Hi - yes, my DS1 didn't start to walk until he was 26 months old. He has hypermobile joints. We were referred when he was still not walking (and showing no particular interest in doing so) at 18 months. We saw a consultant within 6 weeks I think - 18 weeks seems like a long time. She also referred us to the paediatric physio team at the local hospital.
He sat unaided at 7 months, was late to crawl (14 months i think) but at around 16 months people started to ask why he wasn't walking and so we got him checked out by GP. GP said that if he wasn't walking he would be referred automatically at 18 months.
I know what you are going through, it is awful. We used to meet up with my NCT group (so children were exact peers of DS1) and the last time we all got together I came away so upset. He was 17 months and sat and played on a blanket the whole time whilst the others ran around, climbed up slides etc. I felt that the fact he wasn't walking was going to impact on other aspects of his development and that was so worrying and upsetting.
Having the diagnosis of hypermobility was really reassuring as it meant there was no reason why he couldn't walk, he just needed to strengthen all his joints to be able to do so - ankles, knees and hips. He was also the world's most cautious toddler and is a bright little boy - the physios said he had probably worked out that he wasn't strong enough to take his weight so had decided not to try. So, once we understood this and knew there was nothing sinister underlying it we were less worried and it meant I could shut people up who asked why he wasn't walking as we had a reason. The advice was to keep him active to help him build muscle tone - lots of crawling up and down stairs - and to get him shoes that gave good ankle support to encourage him to weight bear more.
Then one day, he literally stood up (he was sitting on the bottom step of our staircase) and walked. About a week later he was no longer crawling. He was very steady on his feet and we had very little tripping, stumbling etc. It was like he'd always known how to do it but he'd decided that the time was right! (And it was the in the nick of time as I was 6 months pg with DS2 and was starting to struggle carrying him!)
ANYWAY... to cut a long story short he is now 5 and started school last September. He has just about caught up with his peers in terms of jumping, hopping etc. He is still cautious so this may be something to do with it but we were told by the physios that he would catch up around the age of 4. But other than that, you'd have no idea he was such a late walker. DS2 didn't walk until 18 months - I think he has the same thing but milder and is a different character - but having been through it once I was much more relaxed about it.
I hope this helps, I feel for you. All the best with your DD - you will feel much better when you have some advice. It is horrible to feel that your child is missing out or that you have somehow failed them but if it's the same thing as DS1 then she will be fine and get there in the end, just maybe at a slightly slower pace.