HBsAg & HBsAb (Anti-HBs) both positive

Hi, I have a member in family with chronic hepatitis B, probably infected 16 years ago, when she had the symptoms of acute hepatitis B, including jaundice (she is also positive for HAV antibodies). She didn't know that she was infected with HBV until 2003 I think, when she went to donate blood.
Until this year when I read about HBV, she did only ALT & AST tests. She didn't take any medication.
She is:
HBsAg reactive (3.0 OD, 0.077 cut-off),
HBeAg negative,
HBeAb reactive (0.004 OD),
HBcAb reactive (0.008)
HBV DNA 47000 copies/ml.

This month I was curious to test her for HBsAb (Anti-HBs).
The test was reactive 15 mIU/ml:
reactive > 12 mIU/ml
border line > 8 mIU/ml & < 12 mIU/ml.
negative < 8 mIU/ml.

What could this mean?
Is her HBsAg suffered some mutation?
If it's a mutation, than why the HBsAg it's detected?

Many thanks.

[stevenNYer]

HBsAb is actually found in a decent percentage of chronic B Heppers.  But it pretty much useless since it probably directed against a different HBV genotype or the virus has mutated B-cell epitopes so this antibody cannot form an immune complex to neutralize its true HBsAg.

What's terrible about this situation is that many many doctors don't know about this and they assume that the person is immune or in the "grey area" so on its way to clearing the virus.  This is true for an acute HepB infection.  But if your HBsAg is positive for over, say a year, you have chronic HepB regardless of your HBsAb result.  Yes, having false hope suck...been there.  Hey at least, some of us could answer these question now to establish info on the net.  When I was looking for this specific answer, there was nothing. One of the few times that goggle searches failed.  There was nothing.