Is it Ok to ask about strap-ons via email to a provider if she does not mention it on website? Or is it safer to ask by calling her. Nothing explict, but just wanted to ask her to bring strap-ons and toys to the session. I guess she will understand the rest.....

Providers that have toys as their offering typically with allude to toys on their site. Also, did the reviews of the lady mention toys.

none of her reviews mention this either, then you might want to generalize in an email AFTER you have been screened.  Something like, "Honey, could you bring some of your favorite toys with you for our date?"