Argh. Pet store puppies are left in their little boxes virtually 24/7 and have no choice but to soil their "crate" area. If you got her at 8 weeks she shouldn't have been so conditioned by that as to be the cause of your problems now, though. On the other hand, if she was available for sale at 8 weeks, she probably left mom way too early and might associate confinment with all sorts of nasty things.
Can you leave her closed in one room? Even a bathroom with her crate and litter box in there, along with lots of toys and interesting things to chew? Some people leave a radio or TV on while they are gone to give their dog "company".
I crate my four dogs at night and they all leap into their crates willingly (our bed time ritual includes me sprinkling some bacon bits in their crates for them once they are inside

) but once the bits are gone, my six month old puppy will begin to whine and cry to be let out. Not because he minds the crate, but because he hates to be separated from me. He'll do the same thing outside a door if I'm on the other side of it. He will settle down in a while and go to sleep, some nights immediately and some nights he carries on a bit longer, but he always gives it up eventually and settles in. I bring it up because I wonder if her problem is more that she hates to be confined where she can't get to you, rather than just confined.
At six months she should be able to go four hours in her crate without soiling if you are being careful about her food and water schedule so that she won't have to eliminate while she is confined. Don't always rely on what the books tell you about how long to wait between feeding and crating, watch for yourself what her schedule seems to be. Dogs can differ a lot in how long it takes to digest food, and what they are eating can effect it as well, so be consistent in what she eats before she will confined.
How is she on potty training in general? Does she soil anywhere else in the house?
One last thought...it can be tempting to make a big deal out of letting her out of the crate when you return home...lots of happy greeting and play. It makes getting out a big reward for her....which would naturally make her anxious to get out and get that reward. My morning routine is to open the front door before opening the crate doors and as soon as the crates are open I walk outside without acknowledging the dogs at all. Once they are outside with me they rush off to pee before I will greet them, and by then it's no longer associated with getting out of their crates.