Yellow diamonds in the light
And we’re standing side by side
As your shadow crosses mine
What it takes to come alive
Rihanna might be referring the loved ones as bright yellow diamonds meaning that her love is bright and cannot be dimmed. "We're standing side by side" might mean that they are standing together and their bond will never break. .
That she's falling for him and she will always be by his side even when there apart. This might suggest that she's not going anywhere, meaning that she will always love him.
a body like an hourglass it's ticking like a clock.
It's a matter of time before we all run out,
When I thought he was mine she caught him by the mouth.
I waited
She likes this guys but another girl referred as her 'body like an hourglass' has taken him before she had a chance. She caught him out when she thought he was hers but she got there first.