Internal privacy for different calendars

I am a massage therapist and have just taken on a second self employed therapist to work alongside me.  I have set up a separate calendar for her and have started booking appointments in for her.  But she also needs to have access to book appointments around the ones I am doing for her.  But I don't want her to necessarily have access to all of my contacts.  All of my financials and my calendar - just in case!  How can I do this?  Is there a way of doing this internally within Aquity or is there a way of syncing her calendar only across to google mail so she can see the bookings that come from me there?  I have confused myself and I'm sure there's a way.  Thankyou!