hello!
i'm afraid that early wakeup is all too common at 4 months. it's mostly developmentally related, and it can definitely be extended. that first "nap" at 6am should be part of her night sleep.
have you ever left her to chat to herself (not crying)? sometimes they do just drift back off to sleep on their own. otherwise, you could do pat/shh (or pu/pd if that doesn't work). before you do that, though, i'd try & do wake to sleep, and see if you can just eliminate it altogether.
my 2 cents anyhow!