XD I imagine Zepheera and Donna would have a roller-coaster of a relationship. Donna’s a rather intimidating human for a borrower, being so loudspoken and robust in personality, so Zepheera would be wary of her at first. After a rocky start, Zepheera would warm up to Donna, but the Doctor would be quicker to adjust to having such a small person around all the time (i.e. keeping his voice lower and gentle handling). She and Donna would definitely butt heads every now and then, just like Donna does with the Doctor on occasion. It’s practically how the three of them show affection.
While they have their differences, at the end of the day Zepheera and Donna get along fine because they know exactly what they have in common. They’re both strong-willed and passionate, relish in all the traveling, and they both truly care about the Doctor, a man they want nothing to do with romantically and everything to do with in all other respects.
And I’m sure Doc loves his gals just the same.
Borrowed Time and Space 