I really think it depends on who they have around them, you have three other kids, and so everything is all around to look at and toys will be given to her , saving her the bother!
Mine all got later to start walking as they were subsquent kids, eg number 1 was 12 mths , number 2, was 13 mths and number 3 took 16 mths to walk, and Devon has just turned 12 mths and he is nowhere near, he has only been bum shuffling for about 3 or 4 weeks now!! He can step when you hold him up, but there is no weight bearing going on at all!! He cannot cruise or walk the sofa , pull up yet etc, so it's not going to be soon.
Once Shan walks as a later one, prob like my daughter, she will be walking really sturdley, so at leat less injuries to her face from wobbles!