If you don't have a formal diagnosis from her physician, that might be your next best move. I don't know where you live, but you or someone else that's involved should also look into getting medical power of attorney for your mother. There are a lot of difficult decisions coming up regarding her care and those are preparations best made early.

Remember that many, many people have been through what you and your mother are going through right now. There's a wealth of available information for you. I also recommend that you visit a memory care facility just so you can get some of the pamphlets and other materials that they have on hand for families that are dealing with this.

Finally, thinking of dementia as just a memory problem downplays how insidious it is. It's a loss of overall cognitive function that includes memory, reasoning, and the general ability to think. The only good part about it is that the person suffering from it doesn't typically know that it's happening.

Best wishes and good luck. Your mother is fortunate to have someone who cares about her like you do.