My hair is naturally brown, but I decided to get it highlighted blonde two weeks ago and the lady did an AWFUL job. Is it to soon to dye my hair back to it's original color?

You could probably get it dyed back to your original color now but it might not be exactly the same color because its not natural. It will be very similar if not though!
Believe me I've been there with awful highlights!
When I was 13 I got blonde highlights (I also have brown hair) and they looked horrible, a couple days later I decided to take a swim in my families pool, and believe it or not but my blonde streaks turned green from the chlorine and sunlight, my friends still talk about this and I'm now 18 :(

What is horrible about them? Be more specific! Tell me what color blonde are the highlights? Is it the color itself or the foul placement that was used? Like are they too chunky? Not close to your scalp? Have bleed marks? Be more specific! May have some answers for you! If you really can't handle it yes you can color over the highlights! Depositing color is very gentle to your hair! However let me know the specific things you dislike! Sounds like a 15min fix!