the actress i mean... i forget where i have seen here
I KNOW 2 things that are clear. I'm a great sinner,Christ is a great Savior.
There is no woman who says 'don't go to Russia'. The action of this film begins in 1814, after the disaster of the Russian campaign. You must be thinking of another film.
shareBit of a delayed response but short answer I think you mean: Isabella Rossellini.
I assume you're referring to the YouTube channel History Buffs' episode on Waterloo. It uses clips from the mini-series Napoléon (2002) (which cover's most of Napoléon's life to cover the history prior to the events of Waterloo). The clip is not from the actual film Waterloo. Isabella Rossellini is playing Napoleon's then ex-wife* Joséphine, advising him not to go to Russia.
*Napoléon had divorced Joséphine by that time and was married to Marie Louise. However he was on friendly terms with Joséphine and still confided in her.