Bella, Now would be a good time to refer yourself for some help. Therapy might be the place to start. Also schedule a chat with your GP about how you feel, as it seems your mood hasn’t been good before this situation.
Sorry if this sounds blunt (I’m autistic), but your daughter should not be what feels like your purpose in life. You are a brilliant mum, but you are also a person, and I think you may have lost sight of that. Being menopausal will only add to this. You deserve to be happy and secure, whether your daughter is home or not.
Having children leave home is very hard. Most people don’t realise until it happens. I was beside myself before, during and after, and the worry was surreal.
Naturally you are feeling this worry and anxiety now.
The first part of coping, is to accept what’s coming. You know how capable your daughter is, because you taught her to be, so you know she is going to be OK whether you worry or not. I would suggest making plans to meet up with her, so you have that in the diary to look forward to. Try and make some plans with friends or family to keep you socially active, and know that you will be able to call and text and video chat your daughter regularly. Getting out into the fresh air will help, so brisk walks and regular workouts can boost your mood.
Lastly, do what you need to do. If you want to cry, do that. Mope. It’s allowed and encouraged to help you navigate the strong emotions and upheaval. I don’t need to tell you about my situation, but just know that things will definitely get easier and less painful, and you will cope. There’s no time limit, so process things as long as you feel the need to.