OMG the cruelty of people never cease to amaze me!!

She's old, she's hot, and the most imortant thing is comfort for her. I say shave her but don't go to the skin unless you have to, I'd probably start with a 4 or 5 if you have to use a 7. If your going to shave her learn about wet shaving, it's awesome!! You can shave down a wet clean dog much faster than a dry dirty gritty one, and it keeps the blade cool so no clipper burn, and you can actually clip the hair longer than you would if you clipped before the bath. Though if she is bathed now and clean and her undercoat has been brushed out then you can just go ahead and shave before she gets dirty again.