anonymous, the only Selina from Macclesfield that I can find in this period that I can find who married a McManus (or similar) was Selina Swaine whose marriage in 1865 is shown below...
Name: SWAINE, Selina
Registration district: Macclesfield
Year of registration: 1865
Quarter of registration: Jan-Feb-Mar
Spouse's last name Not available before 1912
Volume no: 8A
Page no: 187
Possible Spouses: Either, MCMANNS, James ...or... MCMANNS, Joseph
This woman appears with her parents in the 1851 census, and her father appears to be connected to the silk industry...
SWAIN, Joseph Head Married M 35 1816 Heward At Silk Mill Macclesfield, Cheshire
SWAIN, Mary Wife Married F 36 1815 Macclesfield, Cheshire
SWAIN, William Son M 10 1841 Silk Piecer Sutton, Cheshire
SWAIN, Salina Daughter F 7 1844 Macclesfield, Cheshire
SWAIN, Emma Daughter F 0 (6 MOS) 1851 Macclesfield, Cheshire
Perhaps the name confusion is the reason why you have struggled to find records ?