If she wrote any riffs/runs/melodies she received writing credits for that. Seeing as it's a cover, I think we can assume she came up with the arrangements and harmonies for their version.
Beyoncé writes riffs? That's part of the production tho.
What Now would've served a Stay tea on a WW scale with a different chorus
i've been ignoring this big lump in my throat
i shouldn't be crying, tears were for the weaker days
i'm stronger, now what, so i say
but something's missing
If you wrote the LYRICS and the MELODY, you are the sole writer of the songs. Words and Music are the two “non-negotiables” in any copyright. The other two elements of songs — the HARMONY and RHYTHM — are matters of arrangement. For example, think about how many arrangements of “Amazing Grace” you have heard — everything from Country, to bagpipes, to symphonic performances — but you still know that the song is “Amazing Grace” because the words and melody are the same. – Songwriting Credits:
So, unless Beyoncé knows how to compose a song (which I doubt since I never saw her even playing an instrument), her vocal runs/ harmonies are part of the production.
You can just tell when she had a hand in writing something.
I didn't even know this 
