The 34-year-old singer and Orlando, 42, announced their engagement earlier this week, and according to an insider, Katy was overcome with joy when the Hollywood star popped the big question.
An insider told People: ''Katy was very surprised and shaking with happiness.''
Orlando - who has an eight-year-old son called Flynn with his ex-wife, model Miranda Kerr - approached the proposal in a traditional way, seeking her parents' permission behind he asked Katy to marry him.
The source shared: ''Katy's family knew he was proposing. He talked to her parents about it before.''
Meanwhile, another source previously claimed Katy is convinced Orlando is the ''right man for her life''.
The loved-up duo - who split in 2017, before rekindling their romance last year - are ''over the moon'' about the thought of married life.
The source explained: ''Katy and Orlando have been looking forward to this day for a very long time and they are over the moon to embark on their lifetime commitment.
''They talked about an engagement even before their break-up in 2017 but Katy wasn't ready. She just wasn't ready at first but soon after some time away, she knew Orlando was the right man for her life.''
Although Katy and Orlando have tried to keep their relationship out of the spotlight, they've been planning to tie the knot for ''a very long time''.
The insider said: ''They have been very hush, hush about it but have known for a very long time they wanted to be engaged. They have been preparing for this.''
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