Capri Anderson made alarming allegations about that infamous night she spent with Charlie Sheen — including claims of alleged drug use and abuse … and she says she’ll file a lawsuit today.

Anderson, who sat down with “Good Morning America,” described Sheen snorting a “white powdery substance” and recounted the moment when she felt things took a turn for the worse, saying, “When I became really uncomfortable is when he put his hands around my neck.”

Sources connected with Charlie say he did absolutely nothing violent.

Anderson — who was there with her lawyer, Keith Davidson — said she plans on filing a lawsuit today in Los Angeles Superior Court.