I think everyone has a good point here. ProfStokes is spot on about the 1840 Angelique not knowing anything about the other timelines save for 1795, and therefore not being as far down the road to redemption as we might think.
But I think Vlad has a point too, the writers seemed to have been moving us emotionally in the direction of sympathy towards Angelique because of her 'helpfulness' in 1897, and what she did for the gang in 1970.
Dr. Lang you could be right - maybe the 1840 Ange IS the one from the original 1795, or she could be from even another thread of time. Who knows why Barnabas forgave her, that's never made a lot of sense to me...unless he thought the forgiveness would help her to rest in peace, so that she wouldn't come back to wreak more havoc in his life. It reminds me of a line from Buffy "Forgiveness isn't given to a person because they deserve it. You give it because they need it."
And of course, Jennifer I have to agree with you too. All this time travel stuff can make my head spin like I'm on nitrous oxide at the dentist's office, lol!