I’m gonna say it’s something obscure like a relay at an Aus champs carnival between the dates of 1990-1995
Does swimming count as running?
Orienteering or rogaining?
Presuming that Blair hasn't got to digitising the family relays' results yet (because 1990 or '91 family relays would have been my first guess) I'm now thinking Aust interclub relays in W21B, but not sure of the year - 1987 or '89?
The one I found was 1994 Australian Relays, W21B (there might well be earlier ones). Jenny was 19, Maureen would have been in her early 60s (she was W60 individual champion that year). Jenny won :-).
Showing that there were some things we don't miss about the Australian Relays being a club rather than state competition, there were two official teams in W21A (and only three of the six runners were actual W21s).
Jenny didn't do so well in Aust Long that year, she had a disaster...something about an early helpers' start - at Cantara!