Is there a way to see who shared a card and who they shared it with? I know the activity log has the who shared the card but I am not able to find who they shared it with.
You should be able to access this through the Activity Log data, but you will need to look at multiple rows to see the all the information. When a user shares a card, there are two separate actions logged: The first user shares the card, then the card grants access to the second user.
It sounds like you were able to find the sharing action by filtering Action = 'SHARED'. To see which users or groups are given access, you can filter to Action = 'ACCESS_GRANTED'. Associated actions will have matching values in the Event_Time and User_ID (the ID of the user who initiated the sharing) fields. In the example below, the John Smith shared the card "Sales Numbers" with Jane Doe.
If this is something you anticipate needing to use frequently, you could set up a dataflow to format the data to all fit on one row so it is easier to reference.