There should be reciprocity in Thai laws.
That woman knows that in Thailand property for foreigners is severely limited, yet she wants to take advantage of English law.
If I were in court I would tell her that since in Thailand a foreigner cannot own houses or land the same goes for her, and that her request should be rejected.
In fact, try to imagine the opposite: a foreign man who is the widow of a wealthy Thai woman, who tries to obtain the inheritance.
What are the chances?