Normal, yes.  Many providers have specific instructions on how to give them the donation, like this one.  Many just ask that you leave it someplace where they can see it w/o having to ask for it, a coffee table, a nightstand, the breakfast bar.....

If this is what she wants, follow her directions.

Swim

is you actually handing money to the lady, which can be interpretted as buying her favors. And yes, it's pretty much the way most ladies would ask you to handle it. Just go with it, we all do.

but it also lets a lady know that you have read her website, and are complying with her wishes.  No doubt the gents that call on me have certain wishes that THEY would like carried out, and I am more than happy to oblige!  This shows a bit of mutual respect.  If you read that part of my site, then I am more comfortable that you read the rest of my "Etiquette" page as well.  It also eliminates any awkward discussion and will ensure that your companion will be anxiety free throughout your date.  This is especially important if you are visiting with her for the first time.
Hope I was helpful!
xoxo,
Alyssa