No need to disprove it! Her assertions on the relationship are not proven.
Seems a very tenouous connection to connect Patrick McGovern the soldier in France to the Duke of Wellington, even though Wellesley was part of the upper class Anglo-Irish ascendancy.
But I'll be pleased if you discover otherwise!
Further to this, I did some online research, and I discovered a Pamela Berry who was born 1912 had the following connections:
Daughter of Captain Lord Richard Wellesley (being the great grandson of the Duke) and Louise Wellesley
Wife of Major Hon. Denis Gomer Berry
Ex-wife of Lieutenant Charles Robert Archibald Grant
Mother of Richard Gomer Berry, 3rd Viscount Kemsley; Antony GRANT and Louise Grant
Sister of Mary Wellesley
Half sister of Major Richard Wellesley
So it would appear the connection (if any) has to be through the Berry/Berrie line, to call it a relatonship is a wee bit of a stretch though!