Have been observing change in vision over the last four weeks....OR HAVE I?!?

Are the new glasses progressive, with different distances for designated levels of vision?  I.e., lower portion of glasses might  be made for a specified level of distance per the script, but the upper portion would just be clear glass (or a different script), if that's what the script required.  E.g., my left lower lens is for something like 25%, the upper portion is slightly different, and the right lens is just pure glass.  

If so, it isn't easy to acclimate to progressive lenses.   A little nod of the head could refocus vision from close to intermediate or farther away.   Crossword puzzles for me require more concentration on a small area, while reading magazines offers a somewhat larger area of concentration.   Still, I've noticed that some magazines are using smaller fonts, so that injects another level of concentration.  

Books (like the Chicken Soup) books are often printed in a more standard script, and for me are easier to read than something with smaller print that might have been used to minimize the amount of paper and cost of printing.   I don't read paperbacks as much as more either, for that same reason.   The print is smaller and causes more eye fatigue.

Did you have the lenses checked for accuracy after they were purchased?  My ophthalmologist offers free checking, so (when I can remember)  take glasses with new lenses back to ensure that they're exactly to script.   I don't have  a lot of confidence in at least one of the big glasses provider.  

I've noticed also that if the glasses aren't perfectly fitted, one lens that's lower than the other can make a difference in sight.  And even new glasses can shift in how they sit on the nose.    

I would take the glasses back to the doctor who prescribed them and ask for a check on accuracy.   That would be my priority next step.

It sounds like the "vision" problems she is having are actually tied to cognition and understanding, not so much to her acuity.

She can see the spot on the floor (her vision works just fine) but can no longer understand what the letters mean (cognition).

Dementia can effect the eyes. Also, the disease maybe progression and they start having problems with the written word.