Questions & Answers about Ella se lava la cara.
Se is a reflexive pronoun. It shows that the subject is doing the action to herself.
- lavar = to wash
- lavarse = to wash oneself
So in se lava, the se tells you that she is washing herself, not washing something or someone else in a more general sense.
With body parts and often clothing, Spanish usually uses the definite article (el, la, los, las) instead of a possessive like mi, tu, su, especially when it is already clear whose body part it is.
In this sentence, se already tells you the face belongs to her, so Spanish naturally says:
- se lava la cara
rather than:
- se lava su cara
Using su cara is not impossible, but it is less natural here and can sometimes sound unnecessary or ambiguous.