I understand that sticking her tongue out a bit seems normal because you did this as a child as well. Perhaps consider taking her to the family dentist and asking if the tongue length is average and if her tongue is connected appropriately to the bottom of her mouth. I have heard of children that have tongues that are connected too far and not far enough. Sometimes that connective tissue must be cut, stitched, requires speech therapy and dental adjustments. Please consider that this may not be something she can naturally control by request.
There is a name for this type of physical condition: tongue thrust. Here is a link with more information...
http://www.righthealth.com/topic/TONGUE_THRUST/overview/h...
http://www.stjude.org/SJFile/rehab_tongue_thrust.pdf
http://www.neohealthservices.com/?gclid=COiI7aLN7pkCFSAgD...
I hope this helps you identify areas of concern. If you do not think it's a physical problem, then perhaps having her do mouth exercises will help her. I think that reminding her multiple times a day will feel like nagging to her. I think this will make her feel very self-conscious if she is reminded of this in a school setting. Children can be very cruel and tease even at 4 and 5 years old. I really think a dentist could help direct you.