English Translation
She is totally selfless.
The English word “selfless” is not the right translation for the word “désintéressé”. It should be translated as “disinterested” or “uninterested”.
I thought you were right, but I was surprised that google translate also says “selfless”.
But wiktionary agrees: désintéressé - Wiktionary, the free dictionary
It’s even at position #1. The more you know. 
1 Like
Indeed, that’s how I would use désintéressé(e) as well.
(The word “altruiste” does exist in French too).
I think I can imagine why it means that.
Think of “interest” in the financial sense. The money you gain by lending someone an amount, and then getting more money back. So your “interest”, i.e. what you’re interested in in this transaction, is your own benefit.
So, if you’re “disinterested”, then you aren’t after your personal gains, and that means you’re “selfless”.
You may well be right, makes sense to me anyway… 