Is there anyway you could walk her longer? Get her really tired out?

You could try a dog cage on the days when you are out for 4 hours, i used to crate mine for that amount of time, and they were fine aslong as they had had a good run before hand.

Could you afford a dog walker? Get someone to take her out and break up her day. Destruction is usually the result of boredom and frustration.

Or you could try and make some sort of indoor pen. That way she has more room, but cant access anything to chew it.

Its not an easy one to deal with.