M.M.
I would be hesitant about letting her cry it out. Since this is a sudden change for you, it likely is due to some factor other than habit, like teething or a growth spurt. My son went through spurts often during his first year and would wake every two hours out of hunger for about a week or so. If it is hunger or teething, then ignoring her is cruel. Look for the signs of teething like drooling, touching her mouth, swollen, gums, etc. If it goes on for longer than a week, it's likely not a growth spurt or teething situation.