IMO, adult dogs can be socialised to over come certain 'fears' or anxieties, especially if they are not too severe. Think of it this way - on a scale of -10 to 10, what value would Sulli have for children? Would it be a -1, -3, -5 etc? You want to work with her to assign a positive value - so a 3, 4, 5 or higher. You can do this by making children exciting and of a high value - take it slowly, but perhaps allow one child to give her a treat or a toy (whatever she likes best). Show her that children are nothing to be feared, but something that can be exciting and rewarding.