I am assuming that means "on French keyboard", not "in French". I have a usa keyboard and live in Canada...Every now and then it thinks I'm typing French and keyboard indeed behaves in a way that some vowel plus some quotation mark indeed gives me some other character (that I don't need :)
That would feel very strange to me. The Canadian layout probably behaves differently, but à is a modifier letter, not two letters. I’d expect backspace to remove the whole letter, including the accent.