This is a very nice collaboration, I am glad to hear it! However, being a musician myself, may I add some suggestions? The difference between your and Saskia's voice in terms of reverb is way too striking, as well as between her voice and the instrumental accompaniment. Saskia sounds a bit like she is singing from the bathroom, so a little more tweaking of the reverb settings should be done, IMO (less reverb). The snare drum sounds too prominent to me and I would take away like 3dB from its level. Maybe you could also use the strings a little bit more sparingly so to allow for more breath in the song, for better climax effect at choosen points in the song, especially when Saskia sings. I think some EQ is needed, too, but it's a bit tricky to determine how much and where when listening from YouTube.
Great job, thanks for sharing! Congrats to you and Saskia!