As Jessika said, this is a huge change for Phinehas. She has lost the only human she ever knew, along with her home, routines, and so on. Lots of grieving as well a a shock - hey, no one asked HER if she wanted this change! She may not realize she CAN trust humans in general. So that trust needs to build and develop.

I also agree with using the Feliway, though others on here have found the diffuser is a waste, you need the pheronomes to be confined more. One room, and work to getting her a collar with a sleeve and spraying on the sleeve (never directly spray the cat) so the calming sense is always around her.

You can also try sitting with some really yummy treats to share with her and other cats. Salmon is a great one. Let her see the other cats interacting with you in a positive way, with no 'hurt' happening.