I agree, she’s manipulating you, and sorry to say, you’re inadvetly encouraging/entitling her by responding to the calls. No doubt it’s happened gradually. Initially one or two calls, you felt sorry for her, and gradually it’s ramped up.
Firstly, put in boundaries. Ie. You are not permitted to take calls during the day, and will not be responding to her.
Be proactive, say if she wants to talk, she can only call in the evening, and only once.
If she starts cry in g, sobbing etc, then tell her to call 111, the Samaritans, the crisis team , gp etc. Have the numbers ready. if she refuses, reiterate that you are not a professional, and unable to help her. If she threatens that she can’t go on then calmly end the call, staying you’re going to call 999 for her as she needs their help, not yours.
As you say, she emotional draining you. If all else fails, block her. You’ve done what you can. She’s a grown up and is responsible for herself.