I was 45 also when my family practice dr. diaagnoised me with a pseudotumor cerebri. I was having migranes daily and head was so foggy I got to where I could not function. Request a MRI/MRA to rule out a tumor or vessel disorder. If this comes back normal then ask if it could be a pseudotumor cerebri . This use to be known as intercranial hypertension. Usually a woman of chidbearing age is suspected of this not someone of 45. I still have migranes but nothing like I did. pseudotumor is in remission. (They do come back just as if it were an actual brqain tumor my neurologist told me.) I never had visual problems with mine other than the natural auras that are associated with migranes. Prayers are with you and your mom. I hope she can be diagnosed soon. It took me years and fortunately my original dr had moved away and I was appointed a new one and she found it my 1st visit with her. That same day she did a spinal tqqp and my spinal pressure was sky high. My neurologist and primary dr of years missed it and so did my optometrist. God's blessings....
Taking imitrex daily is likely setting her up for rebound headaches. I didn't take it daily, but experienced rebound headache before after taking imitrex. If she has not had an MRI (or CT scan) of her brain, her doctor should be ordering one to try to rule out brain tumor, aneurysm, or anything else that might cause headaches. You won't know if it's something like that until you test- so please urge her to get the pictures of her brain!
Is she working with a neurologist on her headaches? If she is and they are the ones telling her to take imitrex daily, I recommend she try a different neurologist. Plus it sounds like they have not done enough testing on your mom. There are many kinds of headaches, but I am assuming she has been diagnosed with migraines, since she takes imitrex daily. Is that correct?