Thanks for posting your query.
Let me know other associated symptoms along with mentioned.
Does she has constipation/ spasmodic abdominal pain/ frequent urge to use washroom?
Does she has burning urination/ increased frequency of urination/ painful urination?
With the available described symptoms, there could be possibility of cystitis in urinary bladder
or gastrointestinal infection
Exact diagnosis could be made only after detailed clinical examination.
She should consult with internal medicine specialist/ general surgeon
and should go for thorough check up.
She should go for ultrasound
imaging and urine routine microscopy, complete blood count
As such weakness of pelvic muscles are never associated with pain.
Meanwhile, she should take antispasmodics, analgesics along with muscle relaxants.