HELP ‼️🤞🏽

I work at a bank, I have the worst shift. 10-7 (I close the bank). Technically they are supposed to have 2 people close together but they don’t. I am 24 weeks pregnant I still have some ways to go but only god really knows. I’ve brought up before to my boss that once it starts getting dark sooner (i live in the mid-West) I would appreciate it if I didn’t have to close by myself and she said “well I cant promise anything.” When do you think I should tell her I NEED someone to close with me bc if I start getting contractions or feeling uncomfortable before 7 I’m not waiting to close the bank I will do it early if I have too 🤷🏽‍♀️ please help.