Sounds like she is peri-menopausal. If you give it time, nature will take it's course.
GP can test her reproductive endocrinology (LH, FSH and oestradiol) to determine her menopausal status, but she only really needs to seek medical attention if she bleeds very heavily and becomes anaemic.
It's important to remember that going through the menopause is a biologocal process that can take years.
You haven't mentioned the absence or presence of post coital bleeding which would put a different slight on the problem, but assuming this is not an issue, then i would agree with the post of NoM.
This does sound menopausal and is quite common and may last for many years....e,g at least 4 years.
LOL...waterboatman.......no! no!.
Your opinion is just as helpful as anyone else......never say never in Medicine because one day one's opinion will return and hit one in the face. It has happened to me many times.