That one is a pretty complicated answer due to the inherently complicated nature of their relationship.
Their very first interaction was Angela saving Angelica and her unborn child from being killed and absorbed by the Pianist when she was without her primary weapons and when her body was weakened as to reduce her ability to fight or flee. So in that brief moment, Angela was like a guardian angel who swooped down and saved her life and her baby's.
But once Roland arrived back in the picture and reunited with Angelica after destroying the Pianist, it would become very apparent to Angelica that she herself wasn't Angela's primary focus. Angela would be pretty blatantly focused on Roland, even if she were also pushing him away because of various complicated emotions. At the start, Angelica in Angela's eyes was less of a person and more of a vessel for her own redemption. In saving some version of Angelica, Angela was able to give A Roland (even if not Her) Roland, the kind of life and happiness that Angela's own actions unintentionally stole from her. Angelica would see Angela giving Roland longing looks, and the pain in her eyes when Roland showed his love for Angelica when Angela was in the room. And how Angela seems both fascinated and saddened when Angelica eventually lets her feel the baby kick. But Angela still never treated her badly, and would be doing all she could to keep Angelica safe and make her comfortable.
Angelica would probably also have her own complicated feelings about the matter, since this is still another woman who pretty blatantly has feelings for her husband. Though overtime as Angela started to show more vulnerability and started to let her guard down a little around Angelica, Angelica would warm up to her more genuinely and want to see her open up more.
On Angela's side, the feelings are probably just as complicated. Her being here at all is both a means of redemption but also a method of self-flagellation. She's giving this Roland a chance at a happy life with his child and the love of his life. That's bad enough. But it's also the sense that this isn't Her Roland. This one never knew her, never got close to her or who he saw bare her heart/bore her heart to her via the Realizations. And since he still has Angelica, if he thought Angela was trying to show affection toward him he'd probably be far more likely to rebuff any open attempts since he's a married man and Very in love with Angelica. Though it would be a very strange feeling for him that Angelica seems to know so much about him and how her icy exterior she tries to put up softens just for him.
From Angela's view, Angelica is her penance. Keeping Angelica alive and helping Roland stay with her is her way of making up for her actions taking everything away from him and giving him so much pain. She was never mean to BE Roland's Angel. That place was originally Angelica's, and it's selfish of her to still want that even though her journey to get here was meant to be a selfless one. But selfishness is still a very human trait. And she occasionally has to indulge herself in that, whether it be brushing her hand subtly against his or just indulging in his kindness to her, even in front of Angelica.
And Angelica herself is also generally a nice person. So anytime she'd try to be nicer to Angela or try to get her to open up, that'd just make her feel worse. Knowing that she'd taking advantage of both their kindness.
It's very complicated all around.