Well, I picked the ten films in which I liked my favorite actress the most, if she had a leading role or not. 
Hope this isn't a problem, Trev. 

Ranked by personal preference of her performance (boy, this was hard!):

1. Le hussard sur le toit The Horseman on the Roof (Jean-Paul Rappeneau / 1995)
2. Damage (Louis Malle / 1992)
3. The English Patient (Anthony Minghella / 1996)
4. The Unbearable Lightness of Being (Philip Kaufman / 198 
5. La Vie de famille Family Life (Jacques Doillon / 1985) 
6. Chocolat (Lasse Hallstrm / 2000)
7. Code inconnu: Rcit incomplet de divers voyages Code Unknown: Incomplete Tales of Several Journeys (Michael Haneke / 2000)
8. Trois couleurs: Bleu Three Colors: Blue (Krzysztof Kieslowski / 1993)
9. Les Amants du Pont-Neuf The Lovers on the Bridge (Leos Carax / 1991) 
10. Mauvais sang The Night is young (Leos Carax / 1986)