"Yes, you must phone her."

Translation: Oes, mae rhaid i ti ffonio hi.

[Moira582602]

Why is it not "oes, rhaid i ti........" ?
Why does "mae" appear? I'm confused, being a bear of little brain.

[ibisc]

The mae is optional here.

[YmaSmitty]

i wondered too-that 'mae' seems to be a flexible word--sometimes there, sometimes not. Says Piglet.

[AnCatDubh]

Why is it ‘ei ... hi’?

[EllisVaughan]

Because the sentence is referring to a woman.

[AnCatDubh]

I mean, why does it need both ei and hi?

[ibisc]

... ei ffonio could refer to phoning him or her. ...ei ffonio hi and ...ei ffonio fe make the 'him' or the 'her' clear to the listener.

[susanescott]

I am confused. My version does not show "ei" anywhere.

[EllisVaughan]

The sentence doesn't necessarily need it. "Oes, mae rhaid i ti ei ffonio (hi)." (with the "hi" almost always being included otherwise it could also mean "You must call him" as well), would be considered the more correct way, at least it is what is traditionally correct. However "Oes, mae rhaid it ti ffonio hi." is now a common enough, and acceptable enough alternative that both are fine. You simply have been shown the version without "ei" due to Duo's system.