I'd wait 2 days then message her back saying
(meanwhiles shes wondering why isnt he messaging mee back!!)
You:"Yes!! your right. How have you been"
Her: good and you?
You: Great, like tony the tiger. *props to supaflya3*
Her: *this is where it gets tough for me* she could write back with a LOL in this case, i'd message her back saying "I'm not a fan of the message tag, What's your number kiddo? I promise to only send you 50 creepy texts a day and call at 3 am breathing heavily into the phone
The smiley face wink at the end is KEY, shows you are just joking but serious about getting her number, chicks luv that shit