I don't think Lando had anything to redeem himself for but I think he would think that.

He had the fate of everyone in Cloud City resting on his shoulders and while he personally would have loved to have given Vader the bird and warned Han off he had responsibilities.

If anyone needed to atone for what went on there it's Leia.

Leia who was a leader herself put her emotional attachment to Han before her head.

She knew what the Empire and Vader were capable of more than anyone else (she was personally tortured by Vader and the Empire destroyed her homeworld while she watched on helplessly) but she had too much of her father in her (ergo the choking Lando by proxy scene).

It's interesting that she also chokes Jabba to death too (imagine this gal with Jedi powers).

If Ady's skills grow with each project and he joined forces with some of the other skilled people on here I could see a group who could actually make Episodes VII through to IX becoming a real possibility.

In which case having Leia turn to the dark side is something I could see happening, going by what we have already seen of her.