I have a 2010 flhtc. Wife has problem with the calf of her leg rubbing against it. Can it be replaced with one that slants down like the newer styles? Or is there another fix?

There is an old saying "Don't Kill the Messenger"...

You can get a new wife

OK- seriously,

I've had some passengers that had that and I just had them scoot up on the seat.
Instead of the bars, maybe see if there is a pad that she can sit on and get a different bend in her knee to avoid the rubbing.