Hi Adeala,
You can get the total favourite count using this function

$count = bp_activity_total_favorites_for_user( $user_id );

where you need to provide the $user_id for the context.

For example, to get total favourite count for logged in user, we can use

$count = bp_activity_total_favorites_for_user( get_current_user_id() );

If you are on a user profile and want to fetch the total count of the displayed user, you can do it like this

$count = bp_activity_total_favorites_for_user( bp_displayed_user_id() );

Hope that helps.

Regards
Brajesh