My grandmother had Alzhimer’s, although it wasn’t the primary cause of her death (other complications included diabetes, high blood pressure, and high blood cholesterol). With her, it was a long, slow decline: little bits of ‘her’ suddenly gone, then seeming remission, then those little bits gone again, that time for good. She thankfully didn’t have delusions until the end, but even they were relatively mild: more related to her being unable to keep events/time straight in her mind anymore, rather than paranoid/etc. episodes.
For advice… find the humor where and when you can. Take pictures. Get her to talk about older days, and record her voice. Be sure to keep in touch with your siblings, and compare notes. If there is any chance that you or your siblings will no longer be able to care for her (either she’s gotten too ill, they or you have gotten ill, etc.), look into alternative care now: don’t wait. If you find a really good place that has no problems with taking care of an Alzheimer’s patient (even if they decline in health), you may want to look into moving her into there even before it becomes a necessity. That way, she’ll have time to adjust to the situation, rather than running the risk of a very painful situation arising later. (Not to say it won’t be painful if you do it ‘early’, but it will be easier to manage.) (Also, this isn’t to put down those who were able to care for their relative/friend until the end: but more of the awareness that not everyone has the strength to do so, and it’s best to realize that before you’re burnt out and wind up regretting your actions during their last days.)
As for your question… yes, unfortunately, the chances are they will get worse, especially so if you’re already seeing a decline. New treatments and medications may help: look into the medical schools nearby, see if there’s a way you can get her into experimental treatment, especially if she isn’t responding to what’s already available.
Best of luck.