Monroe is not visible in the back of Angelina's truck when Nick is watching her through the night vision binoculars.
Rosealee says her mother called to get her to visit her aunt who is sick. We find out in later that she and her mother had not talked in 7 years.
It makes no sense for Mia to let Angelina see her and even talk to her but not kill her. Mia is just creating a lose end for no benefit.