Peruse
Mason Industries range of products and purchase a set of 4 shock isolators which can be installed under the legs that support their bed... wander upstairs with a bottle of wine and the box of isolators... with a spiel something like "Hi, I'm new here and live downstairs... and have come to notice that you have a nightly ritual that kinda wakes me up every night. I work in the acoustics industry [yeah, its OK to lie in this instance] and was wondering if we could install these shock isolators so you can have your privacy".
If shes cute, maybe make a mention that you can go longer than 3 minutes [again, its OK to lie in this instance]