Both are pretty rare now, but Danielle is the more common spelling. It also matches the way the -elle is used as a suffix in many diminutives (e.g., cervelle, ruelle, passerelle)

Is -elle still a living suffix in French? I was under the impression that -ette is the standard.

-elle is pretty clearly descended from one of the usual Latin diminutives (also visible in e.g. Spanish tortilla). -ette seems to come from a much rarer one?

There's a fun map on Spanish wikipedia of which diminutive forms are preferred in which parts of Spain: https://es.wikipedia.org/wiki/Archivo:Diminutivos_del_espa%C...

> Is -elle still a living suffix in French? I was under the impression that -ette is the standard.

Yes, both are used commonly. In names, there are Gabrielle, Cyrielle, Annabelle, Axelle, and many others. I am not sure there is any rule.

-elle is not necessary a diminutive. In theophoric names such as "Michelle" and "Gabrielle" it is derived from the Hebrew El, a name for God.

https://en.wikipedia.org/wiki/Gabrielle_(given_name)

Another commenter believes, in Romance languages, that the "-a" feminine gendered suffix is diminutive compared to "-o" masculine or neuter suffixes, but that is not true. Not for Latin, or Spanish or Italian or even Greek.