I DO think that any caps etc to the benefit system should NOT be applied retrospectively - she can't take the DC's BACK now that they are actually HERE, can she?!
That £2k will have to cover rent, food, gas, electricity, water, bus fares to the library to use Internet if she is like me with no local library and her DC's need to do homework, bus fares to go shopping, council tax top-up, clothing, shoes, school uniform, school trips, cookery ingredients for school lessons, possibly preschool costs too, plus any damage to her home that she will have to repair at her own cost if her DC with SN's damages anything, any trips put that she does with the DC's (even a seaside day trip needs saving for for a bloody year when you are on benefits, no bloody fancy flipping holidays). It will have to cover the cost if any costumes required by schools on 'specific' mufti days, nappies, basically EVERYTHING for 8 people.
Which works out as a daily allowance of £8.22 per person to cover all of the above. Could you cover ALL of the stuff on the above list on that?
Bear in mind that this isn't an amount for just food - it has to cover shoes, clothing, their daily share of all the utilities etc, everything written above...
I would find that hard going with just 4 DC's. Admittedly I am disabled, as are 3/4 of my DC's, so that creates extra costs, and I live in the SE, where even HA rented 3-beds are probably dearer than her 6-bed.
I'm just glad that I'm exempt from the cap because DS3 gets DLA.