I think it has to do with the fact that we are describing a skill she has, how well she can do something, so we're kind of speaking in general (thus, not referring to 'now/the moment of speaking'...).... And in such cases in English we'd use the simple present tense.
Hope this helps.
I think the person pronouncing it here uses the z-sound. The ch-sound does not appear in Dutch pronunciation of zwemmen or similar words. Dutch people tend to make the reverse mistake when they pronounce Straße and leave out the ch-sound. It's a giveaway for Germans that a person is Dutch and vice versa.
No, I'm trying to explain why it doesn't sound like swim and what you interpret as a German sch-sound is a actually a z, but with perhaps a somewhat faulty audio. Although many Dutch do pronounce zwemmen as swemmen, like marleinrush noted, it differs quite a bit from region to region. Our w is not like the English w, of course, so perhaps that is why it may sound German to you, either with the s or z pronunciation.