I am not an attorney, so JMO.
I think it is because this witness alone may be sufficent, or nearly so, to convict OP on PM charge.
She may be the only one with the correct # of shots in her police statement.
And her testimony destroys his sworn Bail affidavit in several ways.
1. It negates his claim of not hearing any response from the person in the toilet after his alleged screaming to "get out." The witness has said Reeva did scream aplenty before shots were fired.
2. Oscar's claim of not knowing where Reeva was is also negated by this witness, as her voice would've been known to him before his shooting from those screams for "help."
So IMO because this witness is so damning and near conclusive, and alone may make the case, the Judge is allowing so much badgering of her so DT can try to shake her. JMO
And it hasn't worked.
Stalwart is this lady.
Again I do not believe the Judge will allow Roux so much leeway for later witnesses, but I could be wrong.