i would hold off and wait until she tells you she is doing a wee.. that is the best sign they recognise it! and you dont need to have a blaring thing every 30 minutes to remind you or her(the point of it is she knows and doesnt rely on being told) that she needs to go..

i have one child who i did the timed tting and one who i let decide when she was ready and i can tell you which one has very few accidents and didnt actually take any training (well except to teach her how to get on the toilet) 2 yrs on eldest still has accidents and doesnt listen to his body...