To answer your question about the tip it's a bit steep, but this place also charges a $25 upsell if you want a table shower (unless that changed, haven't been here in a few months). What you said you would do next time is the right move. Forego the $40 upcharge for a few visuals and just do some OTC roaming.
Her massage is good. And agreed, she can take the wind out of you if you like it strong!