Fainting, dizziness and blurred vision post surgery

This the first time I have posted here, and hope this is the right way to do it!
My 15yr-old daughter had a craniotomy to remove a 6cm AVM mass on June 13, 2012. We are still in the early days of recovery and overall she has been steadily improving and regaining some sensation and strength in the left side of her body.
However, in the past two weeks she has experienced dizziness, blurred vision and has fainted. The second time we managed to get her to lie down before she actually passed out. Both times we have seen a dr in emergency and they haven't been able to say why she is expereincing this, other than it probably is part of the recovery process. She has had ecg, her heart was racing the second time, but it showed nothing. She has no infection showing in a urine test and her blood sugar levels were within a normal range. She isn't showing any outward signs of aneamia, but we will have her blod tested for that when we see her GP tomorrow.

My question to you all is: Is fainting a normal part of the recovery process after surgery, or should we be concerned it is indicating something else?
Before the severe headaches and nausea which alerted us to her AVM in early June she had never had a bad headache, never fainted, she was otherwise a very healthy girl.

I know you can't give me a diagnosis of anything, but it would be reassuring to hear from your experiences with fainting after surgery.

Thank you.

E's Mum

Hi E’s Mom. Most ER doctors have never dealt with anyone who has had an AVM. I would contact her neurosurgeon as soon as possible. Did they do a contrast MRI or angiogram on your daughter after surgery to make ceratin all the AVM had been removed? Also, is she on anti-seizure meds for preventative reasons? Please keep us informed as to her progress! She is now on my prayer list!

Thank you, Barbara. yes, they did an mri and angio after surgery and it came back clear :) They want to do the tests again in the next 2 weeks to be certain now the swelling has gone down.
She hasn't had any seizures and isn't on meds for them.
her neurosurgeon is away, but I took her to hospital again today and they did blood tests, but no scans. She isn't showing any nuerological signs or setbacks, her progress of recovery has been pretty good so far so they don't think the fainting is related to the AVM or surgery or seizure, simply that she is a young woman and that she's had a faint. We are seeing our regular dr tomorrow. I will keep an eye on her anyway and see what the next lot of scans say.
Was a bit worried this morning, but she seems to have got better as the day has progressed. Thank you so much for responding to my comment. It has been a roller-coaster ride the past few months and I am sensitive to any signs of trouble!