Violeta - Two bottles, one bladder

Two bottles, each with 1.5 litre of water. One is at the top of the stairs, the other one is at the bottom. Violeta has to drink from one bottle, count to 20, walk to the other bottle, drink again, count to 20 etc. Neverending story :-) Her task is to drink these 3 litres of water without peeing herself but that's an impossible task because she is sooo desperate to pee before the shooting even begins :-D So the main question isn't WHETHER she will wet her jeans but WHEN it will happen...