Changing the names ought to protect them, legally. Otherwise, every other episode of DRAGNET and LAW & ORDER could be suable despite the fact that "names have been changed to protect the innocent (guilty)" when their plots have so often been ripped from the headlines.
What is the legal difference between the disclaimer "this is based on a true story" and "this is a true story" (or however Netflix phrased it) ?
Not a lot, although saying "based on a true story" might give a production company a little more flexibility in having more fictionalised content in the show. The thing is, "This is a true story" doesn't mean every aspect of the plot, or every line of dialogue needs to be an accurate reflection of what really happened, it only means the show has to be "substantially true" and the creators are still able to make changes from life to help the story telling. The credits also included the disclaimer "this program is based on real events however certain characters, names, incidents, locations and dialogue have been fictionalised for dramatic purposes" so it was never claimed to be 100% accurate.
It's gone up to $170 million today!
There are only really 4 things in the show that she can sue Netflix for: the amount of communications she sent, the sexual assault by the canal, the prison sentence and invasion of privacy.
If she sent a few hundred or tens of thousands emails and voicemails, it doesn't matter because both would be a substantial number and evidence of stalking so I can't see how she could win on that point.
The sexual assault would be his word against hers and the onus would be on her to prove it wasn't true and I can't see how she would do that other than giving a very convincing performance in the witness box. Having seen her interview with Piers Morgan in which she repeatedly contradicted herself and came across as being slightly deranged I think a court would find it difficult to believe her.
Whether or not she went to prison wouldn't defame her if Netflix were able to show the behaviour that the series implied lead to the conviction was true. I think there is enough evidence out there from many of her "victims" to demonstrate illegal stalking behaviour and threats.
Finally, privacy would be hard for her to prove because she chose to go on Piers Morgan's show to confirm she was "Martha" and she has subsequently agreed to accept money do public appearances to cash in on her notoriety so it will be difficult to argue that she has had her privacy invaded.
Netflix should be confident of winning the case although they might decide to give her a "small" payment, maybe a couple of million dollars, as that might be cheaper and simpler than defending an expensive law suit.