My bike got stolen and now I have to pay it back?

Right for starters I’ll admit I was stupid with how it got stolen. I work at kfc so I ride to work on a bike to get there. When I got there at 8am I left it outside the back door behind gates and infront of cameras. I’ve been doing this for a year now and sometimes forget to bring it in which wasn’t a problem until now. I left it out there by accident as I’m the manager and had to get the tablet done before 9. It completely slipped my mind and when I found out it was stolen, I reported it to the police straight away they told me to look back on cctv and come back. I couldn’t look at the cctv since I need my boss to be there so I decided to wait for tomorrow which i guess it isn’t a smart idea but I had no other option apart from creating a lousy fb post. At first I didn’t want to tell my mother since her and I have a major rocky relationship and only just got a green light to move out without getting my savings removed (another story). So I decided I should tell her because inevitably if I don’t get the cctv back I won’t get my bike. I wasn’t completely honest with how it got stolen as she would’ve went further then she was already has. Anyways when I told her she went off. Calling me names,saying it’s my fault and that I’m not good with my money as well as demanding to take the savings account from me. This bike was a birthday present. Now don’t get me wrong I was very appreciative of the gift but it would be very different if I purposely trashed it rather than it getting stolen. I know it’s my fault but I just wanted comfort. She then proceeded to continue berating me for 3 hours whilst I tried not getting upset infront of my coworkers. I offered to pay back the original price they paid just so she can stop saying what she was but then she kept rejecting saying I need to buy her a bike with the same value. She never rides a bike only gets lifts everywhere. I just find it a bit unfair that it has to turn into such a big thing with little things always and I want to get out so bad