No seriously, I’m about to wreck it! Go get The Elizas and come back! Read the non-spoilery review here!
Eleanor is totally alive. She couldn’t resist telling Eliza about the spa day stunt with “Stella” because she loves telling stories, especially stories with herself as the heroine. Telling these stories, as Stella, just adds to the Eleanor/Dorothy mythos. Eleanor also revealed how she switched places, causing Stella to be killed instead, although of course she can’t admit the truth, and is still claiming to be Stella.
Did you catch that line about Steadman’s shop burning down? Obviously, Eleanor! The only question is whether she did it wanting revenge but not realizing that Eliza doesn’t work there anymore or whether she did it to rescue Eliza from the fire, the same way she took care of Eliza in the hospital as a child. Either way, totally alive and up to her old tricks.