Can the POA cash these out?

Have they matured and that's why they are being cashed out?

I, personally, think that it is in poor taste to worry about beneficiaries when someone is still living, it says people care more about the money then the person.

Yes. As POA if these CDs are, in the opinion of the POA needed for the care of the elder, the POA can cash them in and put them toward the care of the individual. Meticulous records must be kept of any activity by the POA in money into the elder's accounts and money OUT of the accounts. It is up to the POA to decide what must be done in the best interest of the person. In MY own case I could even CHANGE the POD beneficiary when a CD came do were I to have chosen to. I did not change them. When I renewed them I checked with my brother : "Do you still want D. to get the account in the amount of blah blah should you die". He was competent enough for me to do so. I knew this was his wish and were he NOT to need the money for himself I would have left it in D.'s POD status on renewal of the CD. But as the attorney said to my brother, this POA and Trustee of Trust allows your sister to sell the gold out of your teeth, so be certain you trust her absolutely.
Now, the POA may say that the Sister cannot change the POD on some accounts until that money is the sole money left to pay for her care, and cannot cash them in until that time. The POA can say anything that the principle appointing POA/conferring POA onto another wishes it to say. And this need not be shared with anyone at all.
If your sister is gathering money in accounts into other investments she feels (rightly or wrongly) are better investments, she is able to, but were she to put HERSELF on all those account she could be considered to be enriching herself. Now you are talking court action and all the money that puts up the Lawyers' coat sleeves. When the Mom passes the money will be in the hands of the executor your Mom appointed. That may be your sister or anyone else. That person will divide the remaining money as directed.
How much better it would be if siblings got along. Because if they do not, and do not honestly speak and share in the care and responsibility it is an impossible situation. But, hey, a Lawyer's got to live!
If you want to check for certain in your own area then do attend an elder law attorney about this question. It will take less than an hour of your time to get a few questions answered. Wishing you good luck.

I cashed Moms CDs in. They were not making anything. I had no problem going to the bank and showing my POA and getting access. For me, I wanted the money in one place but Mom only had enough for a year in AL.

If there was enough money, I see no reason to cash them in at this point but maybe sis had a good reason. Maybe she found she could make more money having the CDs someplace else. She really does not need to answer to you. As POA she really is not suppose to give any info on Moms finances. She represents Mom and does what she thinks is in the best interest for Mom.

When it comes down to it, Mom could have cashed in these CDs too if she felt she needed them. Beneficiary only comes into the picture when the person passes.

I would not cash them in until the cash is needed for her care. No point.
But, check the institution to see if they will accept the POA. Often the financial institution will require their own form and will not accept a standard POA.

Yes, if your sister is the financial PoA for your mother and only when mother is incapacitated. Not sure is you know how much assisted living costs per month? It can be substantial depending on where she lives and if she needs additional services. Also, she may eventually need MC or LTC and that's A LOT more money. You need to think into her future. The CDs will mature at some point. If she lives long she'll need every penny for her care, most likely.