Never

"No!" Rebeca shouted through her giggles. "Nnnn...nnOOO. P...plee-aase I can't!"

"Then I can't stop." Said Helen as she began tickling Rebeca's feet. "In fact. Why don't you girls help?"

The other quickly joined in. Cassie and Cassandra who were still holding Rebeca's arms with one hand began tickling the brunettes sides. While Sarah joined Helen in attacking her other foot. Next they decided to kick things up. Or in this case down a bit.

"Hey." Said Helen. "I have an idea. Let's lay her on the ground!" With their numbers, leverage over her, and control due to their tickling. The four girls lowered Rebeca to the ground with ease. Cassie and Cassandra then put their knees on Rebeca's arms so that they could continue tickling. This time with both hands. Sarah and Helen had to hold Rebeca's leg which was okay since they only needed one to tickle her feet.