These could be signs of early-onset dementia, or they could be signs of something else. The only way to know for sure is for her to get a cognitive evaluation. I recommend a place like a large hospital—around me in Pittsburgh it’s the Alzheimer Disease Research Center. In Philadelphia, it’s the Penn Memory Center. They’ll do comprehensive testing, and you’ll be there to help answer questions about changes and your family’s health.
She probably recognizes these things in herself, but even if she doesn’t, it’s worth talking to her about your concerns. “Mom, I’ve noticed that sometimes you seem to have trouble finding the right words or forgetting small things. It worries me a bit, and I’m thinking I’d feel better if we could go to a memory evaluation together.”
The ADHD could definitely explain memory issues, and so could stress or depression, or really any number of other health issues. Has anyone in your immediate family gotten dementia at a young age? She’s still pretty darn young.
In terms of fear, try your best (I know it’s hard) to put the fear away for now. We never know what the future could bring, and we can’t really predict much of anything. I have always struggled with anxiety, so even considering our lack of “control” is scary for me, too!