My cat is outside- and i get really anxious she won't come back...?

If she is outside and you don't know where you can't know that she is ok. Is there any reason why she can't be a totally inside kitty? Other than being hit by a car there are other risk factors for outdoor cats such as being attacked by other animals and contracting diseases or injuries, which can be fatal or very expensive to treat. There are also other people who don't share your love for animals that will hurt or kill your pet. If you can I suggest you make her an indoor only cat.