Sorry for the delay.
is this for personal use?
Are you asking what sentence she will face?
She can only either tell the truth or say nothing in the course of a criminal investigation.
Those are the only two options.
Generally speaking if you cannot deny an offence then you should be making a no comment interview.
With possession of cannabis though a caution is sometimes available if this is a matter for personal use. It depends whether she is prepared to accept that.
Can I clarify anything for you?
Not really. In fact, it would probably sound as though you are making excuses and the police don't like that generally.
If she has admitted possession already then she may as well take the caution.
The evidence will be sufficient to convict.