Yes, that will be the case. There'll always be the choice to decline, and often you'll be able to simply avoid flirting in the first place so you won't even have to make that choice, keeping things purely friendly instead.
That's not completely true. As I mentioned in my own comment above, there is at least one lewd scene that gave no such option to decline. I even tried completely avoiding the girls the entire night to avoid the event leading up to it, but there was never a choice to decline the lewd after the event. Merely the choice of which of the two girls will do it.