14 year olds can work for 5 hours on Saturdays and 2 hours maximum on Sundays. The laws are different if the shop is also part of the family home.
It is perfectly lawful to state leave must be taken in minimum one week blocks, provided she gets all her annual leave entitlement.
"Your employer can order you to take all or any of your holiday at a particular time, as long as they give you the right notice at the right time and take into account certain agreements between you.
The law does not put any limit on the amount of holiday you can take at any one time. This means you are not entitled to take two weeks of holiday at once, unless your agreement or employment contract says you can. This means that as long as an employer gives their employee the right notice at the right time, they could make you take your holiday as they choose, for example, take every Friday as leave until you have used up all of your holiday."
http://www.adviceguide.org.uk/index/life/emplo yment/holidays_and_holiday_pay.htm#can_you_cho ose_when_to_take_holiday