Okay. First thing's first. What kind of giantess is Cindy, why does she want to take an earthling as her apprentice, and what kind of person would her apprentice need to be?
1) She is a gentle giantess. She came to earth after hearing how much less advanced our society was than hers and, feeling sorry for us, she decided to aid humanity's progress in any way she could. She decided to find an apprentice to support her on her mission. She wouldn't intentionally harm a human without a very good reason (ie: self defense), and she would never kill anyone on purpose, no matter what the circumstances. She has a kind heart, and cares deeply for all those around her. To her, size doesn't matter; if it's a sentient life-form, then it's treated with respect and equality. The human that she picks as her apprentice would have to be a gentle soul who would be willing to dedicate her life to helping society.
2) She is an evil giantess. She came to earth after discovering it as a planet whose lifeforms were all much smaller than her and, seeing it as a world that she could easily conquer, she decided to make it hers. She decided to find an apprentice to aid her in her conquest of the earth. After all, every ruler needs a second-in-command. She is truly sadistic, and takes great pleasure in torturing her victims to the point of tears before finally finishing them off. She sees anyone weaker than her as nothing more than dirt, and treats them accordingly. However, if someone surrenders to her willingly, she'll be a bit more generous to them; she'll only keep them as a pet/slave instead of killing them on the spot. The human that she chooses as her apprentice would have to be a merciless and destructive force who would not hesitate to extinguish the lives of anyone who opposed her.
3) She is a playful giantess. She came to earth on a whim after passing by our planet on a vacation across the galaxy. Seeing that the planet's society was so small, and thinking that they all looked like toys to her, she decided to spend the rest of her vacation here. She decided to find an apprentice so that she would have someone to hang out with. It would be too lonely for her otherwise. She doesn't intentionally go out of her way to try to cause harm to people, but she still doesn't mind if there are a few casualties after one of her games. She is only out to have fun; nothing more, nothing less. The person that she picks as her apprentice would have to be a free spirit just like her, and have a lot of energy to spend hours playing games with her.
4) She is an intellectual giantess. She came to earth while journeying through space to make an interstellar map and, finding the earth as a very interesting planet with many unique lifeforms, she decided to spend some time on this planet to learn more about it's inhabitants. She decided to adopt an apprentice so that she would be able to have someone to teach her about earth's society first-hand. She also felt that it would be nice to have someone to teach about her own planet's way of life. She doesn't try to needlessly cause damage to society, but sometimes she can't resist the urge to take something apart and see how it works. She is a very curious type, and greatly enjoys learning new things. The person that she chooses to be her apprentice would have to be someone who is fairly intelligent, and would be able to efficiently explain the earthlings' way of life to her.
5) Other