How can I stop my 5-month-old puppy from waking me up so early?

I'm sorry to hear that you're having this problem with Sadie! Unfortunately, puppies are very similar to babies in this respect - they often wake up early. There is often no way around this other than waiting for her to get older. The good news is, most adult dogs are happy to sleep later and will eventually adjust to your daily schedule - so be patient with her for now :)

One thing that you could try is crating her in your bedroom, beside your bed - I'm not sure where you have attempted to crate her before, so I apologize if you've already done this. This generally prevents excessive whining or barking in the crate, because you are right beside her - so she shouldn't be lonely or upset. But, being in the crate will prevent her from being able to wander around, chase the cat, or find other things to do when she wakes up - so this is a good way of teaching puppies to lay quietly until it's time to get up, even if she is already awake.