[fiestaz]

Honestly, either way is probably a winner.
Fiesta may be a little sluggish in 1.4 auto form, focus is better in this regard. Otherwise they are as reliable and safe as each other.
I’d personally go the focus for the bit more space and power.
If they both have Bluetooth and good stereos (I know the fiesta definitely had a great stereo) then I’d say it’s purely which one she likes more.