For me, sister and daughter who recently had their holiday here in the UK, I received only one email from Manilahub saying that the visas had been dispatched etc.

Wait till you have documents in your hand.

My daughter's visa was granted a month before the school starts in the PI so it wasn't a problem at all. I would suggest you ask your mum to inform the school about the travel plans like what Rayna said. How many weeks she will be off, purpose of travel and if you could retain a written letter from school about them agreeing the student to be off for certain days/weeks.

Upon the immigration, they will ask any sort of q's so let your mum have all the documents that VFS returned to you, at least she then has all the docus on hand in case they want to see proof.

Goodluck! Hope they both have visas stamped.