Richmond tied for sixth place with rounds of 80, 80 and 75 for a total of 235 over the par-72 course.
She finished five strokes behind the Dutch winner, Nan Croockewit-Roland Holst who scored 79, 78 and 73 for 230.
Jane Rees from Wales was runner-up, two shots behind the winner, with scores of 80, 78 and 74 for 232.
Overnight leader Gertie McMullen from Ireland slipped back to a joint fourth place finish after a final round of 79, her worst of the three, for a total of 234.
Sheena Wood (Aberdeen Ladies) and Margaret Sievwright (Buckpool), the only other Scots apart from Richmond to survive the 36-hole cut finished joint 28th and 35th respectively.
Wood scored 81, 84 and 82 for 247. Sievwright had rounds of 83, 86 and 81 for 250.
West Vet May Hughes did not make the cut for the final round
SPANISH SENIOR WOMEN'S AMATEUR CHAMPIONSHIP
Isla Canela GC, Ayamonte.
LEADING FINAL TOTALS
Par 216 (3x72)
230 Nan Croockewit-Roland Holst (Ned) 79 78 73.
232 Jane Rees (Wal) 80 78 74.
233 Jo Shorrocks (Eng) 75 82 76
234 Maria de Orueta (Spn) 77 82 75, Gertie McMullen (Ire) 77 78 79.
SELECTED TOTALS
235 Maureen Richmond Sco) 80 80 75 (T6).
238 Aileen Greenfield (Eng) 75 83 80 (T10).
239 Angela Jones (Eng) 78 81 80 (T13)
240 Debbie Richards (Eng) 80 84 76 (T16)
241 Helen Lowe (Eng) 81 79 81 (T18).
245 Sandy Catford (Eng) 86 84 75 (T25)
247 Sheena Wood (Sco) 81 84 82 (T28)
250 Katharine Russell (Eng) 86 86 78, Margaret Sievwright (Sco) 83 86 81, Kate Evans (Ire) 85 80 85 (T35).
258 Marilyn Henderson (Ire) 88 88 82 (T55).