Expenses in groups are visible to everyone. Groups are intended to allow a group of people to have a shared account that shows everyone their status. Because we want everyone to have the same experience looking at the group, we hide personal expenses from the group. This makes sure anyone can double check our math and avoids invading anyones private expenses just between friends.
To settle up specifically in your group, you can register payments from the group and have them visible there.
To fix all balances between your groups and friendship, go to your friendship, click on the gear near the name at the top and simplify expenses, which will leave a note in your group that the debt got moved to your personal account, but would not violate your privacy if you are uncomfortable with the group knowing your exact status.