Vistale

Appreciate any help on this frustrating issue:

My wife recently came to visit me, but was given a B2 visa instead of
a H4 (I'm on H1). Is this normal? She came twice before, first with H4
to visit me, the other with B2 for a conference. She has a job in UK
and on the application form she wrote that her intention was to visit
her husband and would stay for a month or so. Was the length of stay
the reason they gave her B2? This time I want her to stay, but how do
we go about changing her status to H4?

Can we make the change in the states by filing I539? But how do we
state the reason of this change? I am afraid whatever we say will
constitute some sort of fraud. We definitely need some advice here.

I also heard the other option--to change outside. But what's the
difference? We still need to tell them the reason for the change,
right? Besides, what are the new rules of applying a visa in Canada or
Mexico?

Thanks a lot for any advice.
Vis