Hi B.:
I had this when I was 30 ( I am now 44)---it can have a range of symptoms and can be a cyst or type of tumor.
The MRI will likely be a contrast MRI where they give her a shot of gadolidium which will highlight the area they are looking at--it can sting slightly but does not cause any other trouble--they may actually have a better contrast dye, today.
When I had mine done in 1995, they removed it surgically through my nasal cavity---this sounds scary but is the least invasive way as the sinus cavity is right in front of the pituitary. They make a sealant from the patient's blood and close up the hole--the surgery is done by scope so it is easier on the patient. I was in the hospital for 5 days and they made me drink a ton of water and take a low dose of cortisol until the pituitary "woke up." They usually put packing in the nose and then take it out after a few days. I was on IV antibiotics in case it was a cyst containing bacteria. Mine contained acne bacteria and probably happened from picking my face when I was younger---(bacteria tend to find the place in the body where there is space---the cavity where the pituitary hangs is one of the only open spaces in the body. This is why people with knee/hip replacements and other hardware take antibiotics before dentist visits)I should have listened to my mom! They will let you know what it is and then develop a course of treatment--these are a lot more common than one would think.
Recovery was around 4 weeks, including the hospital stay and during that time you don't bend over or lift anything.
Dr. Peter McLaren Black at Brigham and Women's is one of the best for pituitary growths--he developed the trans-nasal procedure with Dr. Nicolas Zervas from Mass. General. Dr. Black is a wonderful man and very good at what he does--
I hope this helps a bit and I am sure that your daughter will come through this just fine--I know how scary it is but there are great doctors who know what they are doing with these conditions.
C.