The syllogism in question is not valid. Nothing logically guarantees that the set of single girls and the set of sad girls overlap. Even if both sets have members, it does not follow that they have any members in common. Compare: Some polygons are squares. Some polygons are triangles. But it is false that some polygons are square triangles.
The syllogism in question is
The syllogism in question is not valid. Nothing logically guarantees that the set of single girls and the set of sad girls overlap. Even if both sets have members, it does not follow that they have any members in common. Compare: Some polygons are squares. Some polygons are triangles. But it is false that some polygons are square triangles.