Seager and her husband settled in Adelaide in 1908. The following year she established her own business, the Scholastic Agency, which placed governesses and servants in employment in the country. When the first South Australian contingent left Adelaide to join the First World War in August 1914 they drew a great deal of public interest and enthusiasm. However, when Seager visited her son, who had joined up, at the Morphettville military camp in November 1914 she was surprised to find that they had not been feted in the same way. She was determined to do something to support 'our boys' who were going away to war. With the support of William Sowden, editor of the Register newspaper, and a number of other women, Seager established the Cheer-Up Society. The Society was conceived as an organisation of volunteers, mostly women, who would boost the morale of the troops and to make sure they were fed, housed and entertained. The Society was at first known as the 'Cheer-Up Our Boys Society'.

Members of the Cheer-Up Society visited the troops at military camps and hospitals, providing free food and organising entertainment. Several country branches were founded and the Society also established Violet Day (first held 2 July 1915) as a day of remembrance. Eventually, the Society erected a tent on Elder Park behind the City Baths as both a place from which to direct the efforts of the Society and a recreation and meeting place for servicemen on leave in Adelaide. Money was raised to construct a permanent building, which was opened on 14 November 1915. The 'Cheer-Up Hut' as it was known provided a place where any serviceman could get a meal, a bed and some entertainment. Interstate or country servicemen, who did not have family or friends in Adelaide to provide such comforts, particularly used the Cheer-Up Hut. Seager worked with the Society fulltime from when the hut was established.

All three of Seager's sons joined up and her husband was a recruiting officer. The Seagers' youngest son, George, was killed in action at Gallipoli on 7 August 1915. Despite, this or perhaps because of it, Seager maintained her loyalty to the war effort and most particularly to the troops and wrote patriotic songs and verses which became popular at the front. Seager's other sons survived the war and served with merit; Ernest was mentioned in dispatches and awarded a Distinguished Conduct Medal and Harold attained the rank of Major. Seager also supported the establishment of the South Australian Returned Soldiers' Association; a grant of 50 was given from Cheer-Up Society funds.

The Cheer-Up Society's operations drew to a close during 1920 and the Cheer-Up Hut was sold to the Railways Institute. Seager went back to her business, although during the Depression she was involved in welfare work again, providing meals for the poor. Seager and her husband retired to Kangaroo Island where their son Ernest had been provided with land by the soldier settlement scheme. The Cheer-Up Society was revived during the Second World War, but Seager was not involved.

November 1914: Established the Cheer-Up Our Boys Society, later the Cheer-Up Society

14 November 1915: Saw the opening of a permanent Cheer-Up Hut

1915: Compilation of poems Cheer-up souvenir to our boys published

1919: "Men" : a collection of verses written during the war published

Cheer-Up Society. Records of the Cheer Up Society Incorporated, SRG 6

'Cheer-Up Society founder dies', The advertiser, 13 March 1950, p. 3, col. d

Mills, Frederick J. Cheer up : a story of war work, Adelaide: Cheer-up Society, Board of Management, 1920

Seager, A. "Men" : a collection of verses written during the war, [Adelaide: A. Seager, 1919]

Seager, A. Cheer-up souvenir to our boys : [poems], [Adelaide Cheer-up Society, 1915]