I’m sorry to hear about your co-worker. I think it’s best to celebrate their life as best as you can. Talk to friends or family and just get off your chest what you feel like you need to say regarding your co worker. Cherish any good moments you have and bring up good times you’ve had with them to keep their memory alive.
I took a job to cover for a woman who’s 12 year old daughter had cancer. My job was meant to be short term, but her daughter took a turn for the worst and I ended up there for nearly two years. Her daughter passed and she returned to work. I listened to her, I let her cry in front of me, I gave her advice and encouraged her to open up to me if she was comfortable with it. We are still great friends to this day. We spoke a lot about her daughter and I think it was important we kept her memory alive and spoke about her so much so my co worker wouldn’t feel like everyone had forgotten her. I hope you can find someone who will be there for you as you take in this loss. Maybe you can confide in another coworker who knew them as well as you did and you can support one another.
It’s hard to lose people from your life, no matter how close you are to them. But I really do find that it is best to talk to someone about it and let everything out that you are feeling. And talk to someone that you know will listen and support you.