get a humane trap from your local animal shelter
than once you catch her   it is going to be a slow introduction phase

You can start by staying near the area where you feed her so that
she must approach in order to eat.  If she is hungry enough, your
presence (around six feet away or more) won't stop her from
dine & dash.  Eventually, she might stop dashing, and you
can also be a bit closer to the food each time....it will take a
few weeks, perhaps...but eventually you can set her plate down
closer and closer to the door of your house.  If she is very young,
she will be more approachable faster since she hasn't been
around long enough to really become seriously fearful of humans.

One day, you might then be able to set that plate of food down
right in your doorway....and then things will go from there.

You can also set up a cardboard box on its side near your door
and place the food plate in there, to attract her closer to the
house.  Once she comes to realize that you are the hand that
feeds her....she may even come closer to you if you start
holding some juicy little tidbit in your hand...it needs to be
nice and smelly so that she can smell from some distance
that you are holding food...see if she will be brave enough
to approach you.

Basically, if you try to think like a fearful kitten who is
overwhelmed by the great big world with no mommy
in it, you'll realize that the security you offer her will
become mighty tempting once you prove to her that
you mean no harm.  Never reach your hand out
directly to the kitten....that will scare her off.  Sit on
your hands, if you need to, so that she will feel a bit
more brave.

Anyways, that was just a few suggestions.

--tension