A dress for Sarah the wedding guest virgin

"Dear Outblush, One of my closest friends from college is getting married in August (Poughkeepsie, NY) and this is my first wedding that I will be attending since I was 7 and I'm completely at a loss as to what would be appropriate! I've scoured the malls since May and I can't seem to find anything! The ceremony is going to be at 3pm with a reception that will go into the night so I'll need something that can be worn both during the day and night. The invitation did not mention a specific dress code, but knowing Rebecca it definitely is not black or white tie. I'd like to buy something that I'll be able to wear again and if it can make my former college boyfriend's jaw drop while looking like Grace Kelly all the better!
Here's the skinny:
1. I'm 5'2" (33-24-33) and usually a 0 or 2 depending on brand sizing
2. Maximum budget: $150 (maybe $200 if it's a classic investment)
3. I'd like something that would be flattering to my shape and about knee length. Probably something that would define my waist; preferably not strapless, but I won't rule it out; maybe something with a v-neck? I definitely do not want something black, brown, navy, or extremely dark. I fell in love with this dress's watercolor floral pattern, but I can't find it in my size. My old roommates used to tell me that my style is classic and girly. I shop at J. crew and Kate Spade the most often.
I know this is super last minute, but if you could help I'd be over the moon! Thanks again. "
Dearest Sarah! Carlota here and I'd love to help you! Weddings are awesome and I'm so excited you want to wear color! You'll actually stand out in the sea of black at the reception. And all of these styles will transition very well from ceremony to reception. Since you loved a watercolor dress, I've chosen a few dresses with pretty watercolor prints in all different silhouettes as well as other blue prom dresses. Hope this helps! And have a great time at the wedding!