Born in Rouen, she was the daughter of Colette Elloy – a 1952 Olympian for France in the 80 metres hurdles. Running for the Stade Dieppe athletic club, she made her international debut as a teenager at the 1977 European Athletics Junior Championships then ran at the 1978 European Athletics Championships, where she competed in the 100 metres hurdles heats only. She rose on the regional scene with a gold medal win at the 1979 Mediterranean Games, succeeding her compatriot Nadine Fricault to the title. Elloy's first national title at the :fr:Championnats de France d'athlétisme|French Athletics Championships came in 1979 and she went on to win five such 100 m hurdles titles in the period up to 1986. In her early career she was a frequent representative for France, but did not make major finals. She appeared at the Summer Olympics in 1980 and 1984, as well as the 1982 European Athletics Championships and 1983 World Championships in Athletics. Elloy began to feature more regularly in international finals from 1985 onwards. She placed fourth at the 1985 European Athletics Indoor Championships then took the silver medal in the 60 metres hurdles at the 1985IAAF World Indoor Games held in Paris, one place ahead of fellow Frenchwoman Anne Piquereau. Outdoors that year she was the B-final winner of the 100 m hurdles at the 1985 European Cup. She improved her best to 12.79 seconds, which ranked her sixth globally in the 100 m hurdles for that year. In the 1986 season she was fifth at the 1986 European Athletics Indoor Championships and then sixth at the 1986 European Athletics Championships – her highest placing yet at an outdoor European final. A lifetime best run of 12.69 seconds in Moscow was a French record that lasted for nine years. It made her the eighth fastest hurdler that season. She gave her best performance on the global stage the following year with a time of 12.83 seconds in the final at the 1987 World Championships in Athletics. Elloy's final international appearances came in 1988, when she was fifth at the 1988 European Athletics Indoor Championships. She ranked third on the 1988 IAAF Grand Prix Final tour. It was also the last year that she won a national title, doing so in the 60 m hurdles at the French Indoor Championships.
International competitions
National titles
:fr:Championnats de France d'athlétisme|French Athletics Championships
*100 m hurdles: :fr:Championnats de France d'athlétisme 1979|1979, :fr:Championnats de France d'athlétisme 1982|1982, :fr:Championnats de France d'athlétisme 1984|1984, :fr:Championnats de France d'athlétisme 1985|1985, 1986
:fr:Championnats de France d'athlétisme en salle|French Indoor Athletics Championships
*60 m hurdles: :fr:Championnats de France d'athlétisme en salle 1984|1984, :fr:Championnats de France d'athlétisme en salle 1988|1988