If she's not having trouble with weight gain, enjoy it! My DD started sleeping through the night last week as well. I have personally woken her up a couple times when it had been 8 hours since I last fed her, because my breasts were going to explode! Consider yourself lucky.
Unless your pedi has concerns about weight- let her sleep! She'll wake when she needs to at that point. I would have paid good money to have a baby sleeping through the night then. Heck, I would have paid it out long after that point with my first, who was a horrid sleeper. You got lucky!
Re: Is it ok to let a 5 week old sleep through the night?
HELL YEA!