If something has been 'found wanting' it means that someone else has tried or tested that person or thing, and that they have has found them to be inadequate or ineffective. In this case, it means that people have learnt through experience that there is something deficient in Mary's character. Perhaps she has shown herself to be dishonest or untrustworthy, for example. Note that this is fairly formal and outdated language which we don't use in everyday conversation. Most native speakers know it from the Bible quotation (Daniel 5:27) "You have been weighed in the balance and found wanting". (I'm totally baffled by Shavingi and Darryl's answers, by the way.)

Here is the meaning of "found wanting": ttps://idioms.thefreedictionary.com/found+wanting "Found wanting" basically means that someone or something is not as good as it was expected to be. Therefore, as if Mary had somehow been found wanting in her character. = as if somehow Mary's character was not as good as it was expected to be.

It means Mary got the character of her choice for acting.

when you are *Found wanting* it means that you have a desire for something, like you aren't satisfied. when you want 4 cookies but you only get 3 then you are *found wanting* in this case, it means she wanted MORE for her character, it wasn't enough.