Success! My friend the ex-stray, but need advice

I want to thank everyone who answered my post asking how to befriend a
stray, and the tips have really worked. During the last week in December my
friend the stray was waiting outside in the yard and as soon as I stepped
outside, the cat approached me cautiously at first, meowing a meek-sounding
"meew" every now and then, and then inched forward slowly until it was
circling and rubbing my legs. This is one affectionate kitty that was
probably just shy or had been mistreated by someone at one time or another.
Then it followed me inside and made itself right at home. Turns out the cat
is female. Vet checkup went okay, the cat is healthy and had already been
"fixed". So far no calls from the cat's owner.

Now I just have one problem: The cat hates me now after attempting to give
it a bath last night. I had wrapped the cat in a towel and gently lowered it
into the warm water, removed the towel, and as soon as I put shampoo on her
back she bolted away with lightning quickness and hid under the bed. When I
approached the bed she let out with the loudest most blood-curdling angry
GrrrMrrrrYrrrow!!! I had ever heard, and even swatted in my direction once.
When I backed away she bolted for the front door and demanded to be let out,
so I let her out, and now she's semi-afraid of me. She'll get no closer
than 50 ft when I call her. When I follow or approach her she'll sit or lie
down but immediately get up and walk further away when I get within 6 feet
of her.

Was it the shampoo? or what? How do I regain this cat's trust? It's cold
outside and I wish she'd come back in. I've put water and her favorite
sardines out in her old feeding spot, along with a cardboard box with a
blanket and old pillow inside of it plus a couple of toys. This morning the
sardines and water were gone, but the toys seem untouched as well as the
makeshift bed. She stays within sight of my house but keeps a safe distance
from me.

Any suggestions on regaining this cat's trust? (P.S. I saw her actually
sitting in front of a neighbor's door earlier as if she wants to be let in,
and those people don't even like cats!)