Honestly you'll be fine. What is it you're actually afraid of?
It will change you as a person, that's undoubtedly true. It may change you in many ways, some positive, some negative, some netural.
Your relationship with your mum will change, it will keep growing and evolving for as long as you're here. Your relationship with her doesn't come to an end just because she's died. Mine died 16yr ago and the relationship I have with my mum now is very different to the relationship we had at the time of her death.
What if you can't cope... you will, because you'll have no choice.
Remember that everyone in this world has lost someone they love or will do, including children, young adults, older adults. It's one of the great unifiers and a natural part of living. You cope because you have to. You'll find your own way of keeping her memory alive and remaining connected with her in time.
Grief is painful but can also be beautiful in a way, knowing that you are forever connected by your love. It can teach you a lot. I learned so much from losing my mum that I took forward into life in a really positive way.
If after a year or so you feel someone to talk to would be helpful you can reach out for bereavement counselling, it helps a lot of people. But until then you need space and time to allow your mind and heart to do what it's designed to do in slowly processing and coming to terms with the loss.
My only practical advise is take lots of photos while she's here, even if they're sad if she doesn't look her usual self. I was only young when I lost mine, early twenties, and we took one last family photo with her in her coffin. I wish I'd taken photos in the hospital but I just didn't think to. Without that photo sometimes it would feel to me like, did it ever really happen? Did my mum actually exist? As it's been so long. But I wish I had more photos.
You're going to be absolutely fine <3