It is very difficult for widows (or any other single mother) to financially support themselves if they have children to look after. This problem is aggravated in countries which do not offer any support to them. SMT Widow Sponsorships aim to ameliorate their difficulties by financial aid to cover their basic needs. Costs vary between locations but are typically between £50 a month.
The Islamic ruling is that after the husband, the responsibility of her assistance and maintenance falls on the son, father, and brother respectively. Failing that for whatever reason the responsibility falls on the community around her. Failing that the responsibility is on the Muslim community in general.