Formal: Elle parle anglais.
Informal: Elle parle anglais.
The only difference is the verb tense:
* Parle is the present tense of the verb "parler" (to speak), which is used in both formal and informal settings.
* Parle is the third person singular form of the verb, which is used for the subject "elle" (she).
So, both options are correct and can be used interchangeably.