I'm sorry to say that a lot of young cats get killed by traffic these days & that is why many people choose to keep their cat indoors with access to an outside run. This not only prevents the heartbreak of losing your kitten to traffic but also prevents her catching various diseases like cat aids from other infected cats & they can never wander off or be 'cat napped' by a neighbour. Failing this I would get all the innoculations, not just the cheap ones, a microchip & keep kitten in until she's been spayed & recovered - usually about 6 month old sometimes 12 months.) Then before her breakfast take her out with you into the garden for half an hour or so then bring her in with breakfast for a couple of weeks. Better to be safe than sorry.