I'm very sorry about your news @mistymirror
Please try not to put pressure on yourself to feel or react a certain way. Shock, disbelief, anger, fear, distress and more are all normal reactions and there is no timetable for you to process or accept any of this.
Hopefully your mum will have support from a Macmillan nurse, and they should be able to link you up with support too. If she has hospice support (even if she's cared for at home she should still be able to access hospice services), they also should have support for you.
I am truly sorry this is happening to your mum. If it offers you any comfort, I lost my mum in similar circumstances and like you it was devastating - but in some ways that final period together brought us closer and after she died over time I gradually found ways to carry her with me still and to cope.
Your mum will always be part of your life, whether she's physically present or not - she has influenced who you are and is part of your story. Relationships don't end when someone dies. You'll be able to find ways to carry your connection with her throughout your life. I never talk about it as "moving on" or "getting over it" because I don't think that's how it works - you don't leave them behind or forget them, you learn to move forward and carry them in a different way. When the time comes, that's what you'll do.
There can be a lot of pressure in circumstances like this to try and get everything perfect - to have all the perfect conversations and moments and bucket list activities. Try not to add too much pressure on yourself and just do what is right for your mum, for you and your family in each moment. It's completely okay to just cry and hold each other or just to want to do little everyday things while you can.
Please make sure you take up support for yourself when you need it. Marie Curie has some information pages about caring for someone with a terminal diagnosis. I won't link it in case you're not ready to read it / it's too upsetting, but that's one place which has support services.
Sending love to you and your family 💐