My boss hen is the same - she crows and has a bigger comb than she should. She only crows in the morning though, just after sunrise. She keeps the other two girls in line as well. She still lays in spring and early summer (but is old so doesn't lay a lot otherwise).
My guess would be that if you got a rooster the hen would revert to being a hen. But I'd only get a rooster if you really want a rooster
At least if the crowing is coming from a hen you can honestly say you don't have a rooster!! I do try to limit the annoyance from my girl though, for the neighbours' sake - she sleeps inside in a cat carrier.
Birds are quite gender bending animals. They are very interesting - a bird can be male on one half on the body and female on the other half (so sex-linked plumage differs on one side versus the other).