Possible Clues:

• Regular girl left
• As usual she gets to fifty
• And neither is Mother getting to fifty, as usual (6)
• Conforming to what is usual
• As usual, she gets to fifty
• There's nothing extraordinary in her being over fifty
• Not usual, and not to be a mother over fifty, either
• 'A mother does not get to fifty, either, as usual (6)'
• She gets to fifty, as usual
• As usual it's the loan about the mister back in there