Not that it matters for anything—she got the work done on the free plan and was happy—but my strategy in this situation is always to subscribe and immediately cancel. The cancellation does not actually take effect until the end of your billing period. (Otherwise they'd have to refund you.)

In my head, I'm not really buying a subscription, I'm just buying one month of access. I can always decide to buy another month if I want to, but it will never be automatic.