If I were in your position, even though this may be your only valid therapy option, I'd speak up about whatever bothered me. Sure, you could lose your only therapy option. But since it's your only therapy option, why not insist on communicating what you need? I would rather do that than suffer in silence.

That said, I don't see why it has to be phrased as "you're doing it incorrectly." Try asking about her methods. Or say, "It would be more helpful to me if..."