How are we suppose to respec if she is no longer there.
Guess you’ll have to press on.
As for why, read conversations next time. 
There will be another one a bit later in the game.
Fuck reading shit hurts my head 
Thanks Stupid Dragon
BTW if you really need to respec badly, you can just head to the next difficulty and then hop back to whatever difficulty you are doing the expansion area questline.
Crucible.
/fuckthechars
Assuming they have bought it, this is also another alternative.
For someone who was in the opening cinematic, Sahdina barely ever did anything in the actual game… so I don’t mind that she got replaced.