This might be due to incontinence or a urinary tract infection. If its incontinence there are meds that can help and of course there are antibiotics to clear up urinary tract infections.
If this is a big issue (like she sleeps in bed with you making a big mess) then you can put a diaper on her overnight just cut a tail hole or you can use a product like these britches with a human stick on incontinence pad in them
www.brownkennelsupply.com/petp05.htm
This is just while you work on resolving the problem.
You should see your vet about this though.
Hope this helps you!
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