Ariel Winter Shows Off Major Cleavage in Cutout Graduation Party Gown, Showers Sister With Praise

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Ariel Winter is a grad with gratitude!

The Modern Family star showed off her figure in a cutout gown on Instagram, while thanking her sister Shanelle Workman -- who is also her guardian -- for throwing her a celebration to commemorate her high school graduation.

"Couldn't be more grateful to @shanelle_gray & @davidbarrygray for throwing me the most amazing graduation party ever last night," the 18-year-old actress wrote in the heartfelt post. "The amount of love and support they've shown me for the past four years has been life changing."

"My sister is my absolute best friend and my everything," she continued. "I was in awe last night and I still am that you guys love me that much to do all of that for me...I never would be where I am today without you guys saved me and taught me to be the person I am today."

WATCH: Ariel Winter Graduates High School in Chic Nude Dress: See the Pic!

Winter also thanked her father in the post, writing, "Dad...I love you!!! Thank you for always being there to support and love me as well and always put a smile on my face no matter what :). I'm so grateful for the bond we now share."

It's been all caps and gowns of late for the actress, who shared a snap from her friend's graduation party last week.

MORE: Ariel Winter Celebrates Her High School Graduation in a Lacy White Dress

"Family ❤ None of this would ever have been possible without them," Winter wrote on the day of her ceremony. "So grateful! ❤️❤️❤️ #graduation."

MORE: Ariel Winter Shares a Racy, Cleavage-Baring Easter Photo

The TV star is attending UCLA in the fall.

Watch the video below for Winter's chic grad fashion.