H cannot force her sell the former matrimonial home, but if they cannot agree how to split all the assets (including pensions) and liabilities solely and jointly held either party can apply to court and a judge has the authority to order the sale or transfer of property and payments of money.
When sharing assets there are a check list of factors in s25 Matrimonial Causes Act 1973 and the welfare of dependent children is a priority. However, they aren't the only FMH be kept for children when it is larger than required and leaves the other parent destitute.
Your friend and H would be well advised to remain realistic and come to an arrangement between themselves that works for everyone or use a mediator. Trying to secure the best possible deal for oneself at the expense of the other party usually results in expensive legal bills and long term damage to family relations.