Growth spurts can certainly drive real hunger that makes kids beg for food all the time. I see it at times too. But....
The fact she is lying about what and where she eats is a red flag. It shows she is well aware that you don't want her having those extra snacks and she is willing to cover up the fact she had them because she doesn't want to get you mad and she wants to continue having those snacks. Be sure your reactions to those extra snacks aren't excessively strong. (How are you finding out about them, by the way, if she's lying?) I'd deal with the fact of the lying and focus on that, more than on the fact she ate something -- for now. And get the word to her playmates' moms that she isn't allowed to snack, or that you will provide the (healthy, low-cal) snack for both kids yourself even if the playdate's not at your house -- any mom who's offended doesn't get it.
Look at what she's eating, not just how much and when. I won't even touch the idea of sweets - I'm guessing you've already stopped those or cut them way back. But if she likes starches (bread, rice, pasta, potatoes), that's fine, but starches break down in our bodies into sugars and things like white bread, white rice, white pasta break down in the body quickly -- and leave us full at first and much hungrier much faster than if we eat whole-graiin starches. Whole grain starches break down more slowly and you feel fuller longer, plus they retain more vitamins than "white" or even "enriched" grains.
Even with whole grains, be sure she isn't eating too much pasta, potatoes, bread etc., because they have heavy calorie loads but kids love them -- and it's so easy to dole out big servings of them when small ones would do. If she eats (you've heard it before, I know, we all have!) high-fiber foods like more vegetables and fruits she will feel full and not have the "crash" and hunger that comes with loads of "white" starches. I'm not anti-starch! It's just so easy to end up basing every meal around them -- cereal or pancakes for breakfast, sandwiches for lunch, pasta for dinner, starchy snacks, all in the same day.
Another thing -- try to teach her to wait 20-30 minutes after eating. That's how long it takes to achieve a "full feeling." This will be hard - I still remind my 10-year-old when she begs for more after a snack that she IS full enough but doesn't feel it yet.
Ask your pediatrician for ideas, and if she's in kindergarten, talk to the school counselor (without your daughter there) about the lying aspect of this. If she does not lie about other things she does when away from you, and the lying is centered just on her eating, you may want to ask the counselor for ideas on how to talk to her about eating as well as telling the truth about what she does -- whatever it is, eating or anything else -- when she's not with you.