I'm pro "extended" breastfeeding, but 5/6/7/8 is beyond extended to be honest.
I personally feel that she is unable to let go and accept her girls aren't babies any more.
I feel breastfeeding should go on until around 12-18 months and that 18-36 months is acceptable, but that weaning should have occured by 36 months.
by the time a child would be off formula and fully onto cows milk and real table food.
you can have the closeness and cuddels with your child without them sucking boobie.
It's kinda hard to say that because as I said I am very pro breastfeeding but I guess you have to draw the line somewhere... and she hasn't even got the pencil out the case yet let alone started drawing.