It seems as if Maya is currently incontinent, meaning that at rest, she loses urinary control. There is a mechanism in place via the autonomic nervous system that kicks in to provide urinary control while at rest or sleeping - a sphincter valve called the internal urethral sphincter. Occasionally in large breed dogs, this mechanism gets weakened and the sphincter loses its tone and the dog wets her bed without realizing it.
However, since you report that she had one other episode where she went to another room and consciously urinated, we must consider the other possible cause for weakening of the internal urethral sphincter - inflammation from some form of lower urinary tract disease, such as urinary tract infection or pH anomalies in the urine that lead to the formation of crystals or stones.
As such, I would suggest scheduling a visit with your veterinarian and bring a urine sample, collected mid stream as Maya is urinating (in a dishwasher clean container). If there are no signs of urinary tract disease, then you may treat incontinence with a medication called Proin. In the vast majority of cases, Prion treats primary incontinence quite well, however, the patient will need to remain on the medication for life.
If the urinalysis reveals lower urinary tract disease, then treating the issue will likely relieve the problem. In the case of a simple urinary tract infection, a course of antibiotics should clear it up. In the case of crystals, prescription diet is usually quite effective in controlling the problem.