Civil Registration Indexes (Births)
Probably:

Gladys Eva Marden, reg. 1st quarter of 1896, Portsea Island, Hampshire, England.
Gladys Eva Marden, reg. 4th quarter of 1903, Rye, Sussex, England.
Gladys Mary Marden, reg. 3rd quarter of 1905, Sherborne, Dorset, England.
Gladys Marden, reg. 4th quarter of 1909, Battle, Sussex, England.
Gladys May Marden, reg. 2nd quarter of 1910, Romford, Essex, England.
Gladys D. Marden, reg. 3rd quarter of 1910, Gloucester, Gloucestershire, England.