With the latest resignation of Jane Philpot this is no longer just about SNC-Lavalin. She mentioned the environment in her letter so it seems she may be dissatisfied about more than just SNC-Lavalin.
Aside from Freeland these two women are the most high profile female Liberals in caucus.
This could bring Trudeau down, not SNC, 2 powerful women quitting cabinet based on ethics.
Philpot's letter is very condemning. Both women know they are giving ammunition to opposition parties against Trudeau specifically. By remaining in the Liberal Party and declaring themselves Liberals they have created an unofficial show-down. It would be very difficult for Trudeau to kick either one out of the party yet he clearly does not have their confidence.