Sorry, I disagree with all the guys on here, she's just having a bit of fun, being cocky etc. nothing crazy lmfao. She's not "testing" you or somehow challenging your frame, just go with the flow and keep bantering. IMO this is the type of girl that's the most fun to text/meetup etc. - they tend to like to have fun and invest quite a bit.

I would respond with something like "I don't want to intimidate you or anything but I won my 3rd-grade spelling be so.." alternatively, you could try "So you're not just a pretty face?" - a bit more ballsy this one but I've used it a couple times and it elicits some pretty funny responses (in a good way).

Hope this helps bro.