I got Sylph of Life and my sis got Page of Life. I'm thinking that would actually be a really powerful player combo in a session - what do you think they'd br capable of together?

Hard one to answer, you two could definitely be a powerful combo, but it would depend heavily on /how/ you combined your efforts and how you acted! Pages get Served their Aspect, so it’d not be hard to imagine you as a Sylph basically pocketing your sister, Healing and Buffing their abilities to bring out the full potential of their power! A beacon of Life, and powered by a Sylph, I feel a Page of Life powered up like that would be able to do Anything they put their mind into (Agency), heal their wounds non-stop (Life), and have anything living (Plants, Animals), serve the in their cause. That sounds kind of badass.