You'll prob be looking at anywhere between 12 and 17ft
im guessing shes around 6 atm, but that can vary on individual, the only thing ill say to be careful of would be when she gets a bit thicker, try and make sure you always have someone with you when you handle her, my friend had a 13ft retic and im sure you've noticed they have a strong grip! he was handling it and i guess the snake didnt feel very secure(being so long and only handled with two hands) so it tightened round his chest and he couldnt get the fella off, it wasnt the snakes fault it just felt it was gonna fall.
do you have any pics of her?