I think the doctor won't suggest CT scan, more likely MRI since
MRI is capable to locate very small problems like small veins being
suppressed by blood clot, etc.
Yes, parental consent is needed if she's below 18 years old. Even
if she's is above, I think should let her parent know since MRI
scans is pretty costly.
However, if like you've said, she's being referred to Alexendra, I
will actually say that SGH will do a much better job. Cause
Alexendra's Hospital resources are very limited.
May I ask whether the actual reason your friend doesn't wish to
inform parents is due to Financial Constrains or ? If we know the
real reason behind it, we might be able to offer solutions.