Explanation:

- The eight girls are seated around a circular table facing outwards.

- B is second to the left of D.

- F is third to the left of B.

- A is second to the left of F.

- C is second to the left of A.

- G is third to the left of E.

- In the potential groups, the commonality must be identified:

- Option 1: A, C, E - These girls do not have any specific direct relationship in the seating arrangement.

- Option 2: D, B, H - These have some adjacency relationship in the arrangements.

- ? Option 3: D, H, G - This option places girls in positions that are directly related.

- Option 4: C, E, F - These girls do not have any direct relationship similar to option 1.

Therefore, the group that doesn't belong is Option 1: A, C, E.