My Mum has CLL. She was diagnosed nearly 10 years ago, in her 70s, after catching Pneumonia. She did have a blood transfusion and chemotherapy, however they said she had probably had it for years before and not known. It's not a cancer that can be cured, just treated if necessary.
Since then, she has had 6 monthly appointments (phone and face to face) with the consultant and had her blood checked each time. She has also had a couple of CT scans.
The tests do show that it is edging back, but it's not causing her any symptoms so she's continuing in watch and wait. If she did need treatment, it would be tablets, but even then they might decide the benefits aren't worth the discomfort it would cause and might just treat any symptoms she has instead. CLL isn't usually life limiting.
The only thing to watch out for is that she doesn't get an infection/illness as she is vulnerable so important to get vaccinated.
Having said that, both times I have had Covid, I had unfortunately spent the day before I knew I had it in her company and she didn't catch it!
It sounds very scary, but isn't really. I know how you feel though - leukemia sounds terrifying.