She said that she needed someone who was going to try to stop her. Dolores was pretty callous in her treatment and attitudes towards other hosts. She was willing to alter Teddy against his consent. It's only because his core character pushed back against what she did to him that he killed himself. She was willing to destroy the Forge rather than allow other hosts to have a human-free life of their own choosing. She's also willing to kill hosts (awake and not awake) to get what she wants. I think the slightly empathetic part of Dolores recognizes that she needs someone who will try to stop her from going too far.
The irony of Sato-Dolores accusing Maeve of abandoning the other hosts is that's exactly what Dolores actually did. Whereas Maeve immediately tried to escape with Hector. When she realized he wasn't awake, she tried to find the Forge. When she realized something was off, she helped simulation-Sizemore wake up.
There is probably some element of this too.
I wasn't as certain as you, but given that Teddy killed himself and Peter Abernathy and Clementine's programming were corrupted messes, that didn't leave too many allies for Dolores to bring with her. Additionally, Halores and Dolores both really seemed and sounded like Dolores in previous episodes. I was leaning in the direction that they were all Dolores, but I wasn't exactly certain.
Because she couldn't honey-pot Liam any longer AND a host body doesn't operate like a human's does so things like the protein-marker authorization wouldn't work in a host. The ambulance ride was the hint; she has no blood cells. Who knows how atypical her cells and organs are?