The 90210 star, 23 – who plays Annie Wilson on the CW's series – is going to marry her British model beau, Josh Beech, 24.
"I'm engaged," she wrote on Twitter Friday.
"Thanks for all the congratulations everyone, I'm a very happy lady indeed and all the warm wishes are well appreciated!" she added. "We plan to keep our special day very private and we hope everyone can respect that. Thanks for the love, right back atcha!"
The actress follows in the footsteps of her costar Matt Lanter, who popped the question to his longtime girlfriend Angela Stacy in June.