:::::::::::::::On the strength of access to the diaries, I'm happy that she can fairly be described as lesbian (as opposed to "probably a lesbian").  The chaste aspect, therefore, is not relevant to this article (it is to hers though, where it really should mention that she was chaste until about 1980).  My only niggling concern is the phrasing in the interview ("from about 1980", rather than "from 1980"; it seems to me likely that a biographer would remember such a salacious date with a fair degree of accuracy).  Not a big deal though, so I'd recommend effectively the same text as Roscelese initially supported, with the interview cited (and Sauvat, if the editor adding personally sees it): 
 :::::::::::::::Jeanine Deckers (d. 1985) was known as The Singing Nun or Sœur Sourire.  She was a Belgian singer-songwriter and was at one time a member of the Dominican Order. After leaving the order, she began a lesbian relationship with Annie Pécher.