Ariel Winter -- UNITED FRONT with Big Sister [Photo]

Ariel Winter sent a very public message to her mother ... she's STANDING STRONG with her big sister and temporary guardian Shanelle Gray.

In a major show of support, Ariel clutched her sister's hand as they walked into a hair salon in Los Angeles earlier today ... and, of course, it was all captured by the paparazzi.

Ariel's mother has accused Shanelle of using the "Modern Family" actress as a "stepping stone" to launch her own acting career. She also claims Shanelle might blow Ariel's fortune on herself.

Shanelle claims she's rescuing Ariel from a physically and emotionally abusive mother.