Dragon Ball Z's Cell Saga wraps up nicely, but it has an oddity to it. After using their first wish on the Dragon Balls to revive Cell's victims and learning that Goku wants to stay in Other World, the Z Fighters are left with one free wish. Krillin opted to use the wish to turn the androids back into humans; when this doesn't work, he instead wished for the bombs to be removed from their chests. Despite this kind gesture, Android 18 snapped at him for doing it. This came off as ungrateful at first and while the two eventually worked things out, perhaps there's some justification for this indignation.
Krillin's wish to make the androids human is kind of a unilateral decision. While becoming a human again might be nice, it would also mean losing all of the cool perks of becoming an android. Even Dr. Gero himself could not pass up such an opportunity. Assessing Android 18's response will require a closer look at the pros and cons of life as an android in Dragon Ball, as well as her ultimate fate.
One of the best perks to being modified by Dr. Gero would have to be obtaining strength and abilities on par with the Z Fighters. There are plenty of people who would give anything to fly around, lift cars, shoot lasers or perform any of the other awesome feats these warriors are capable of. If a person abruptly lost those powers because someone else thought it was for the best, it would certainly be annoying.
There's also the androids' extended life expectancy to consider. According to Dr, Gero, androids have a form of limited immortality. This is the main reason he turned himself into Android 20. Androids 17 and 18 don't look a day older in Future Trunks' timeline, a whole 20 years after their debut, so there may be some truth to this ageless beauty. If Krillin had gotten his wish, 18 would have lost this longevity.
It's worth noting that biotechnological androids like 17, 18, and 20 can still age. They're called androids in the English dub, but they are really just modified humans. It would be more accurate to call them cyborgs if anything. Therefore, their cells can still deteriorate, albeit much more slowly than humans.
For all the positive qualities of being an android, there are plenty of negatives to consider, too. For starters, Android 18 supposedly can't regrow her hair. Whatever style she chooses, she's stuck with it forever.
The reduced aging process could also work against 18. If it's as potent as it seems, then she runs the risk of outliving nearly all of her friends and loved ones by a wide margin. She might even have to watch her daughter Marron grow old and die before she does. Intimacy isn't necessarily something 18 had in mind when she gets mad at Krillin, but that's also part of the problem.
If Android 17's testimony is anything to go by, he and 18 can't experience feelings like humans, either. Part of their transformation seems to be a detachment from their humanity that's very difficult to get back. This would explain why the androids from Future Trunks' timeline go on such a carefree, murderous rampage. It also explains why 17 surprised himself by doing something for someone else during the Tournament of Power, even referring to it as "acting all human." Whatever the cause, there is an apparent loss of both emotion and empathy among androids. If becoming an android means losing one's humanity as well as the ability to feel joy and sadness normally, then it may not be worth it.
In any case, things turned out rather nicely for 18. She's settled down and started a family with Krillin. They even have an adorable little girl to look after together. She seemed entirely content to give up fighting as she only ever does it when there's money involved now. Android or not, she still lives a happy and fulfilling life.
As for whether Android 18 has a right to be angry at Krillin for trying to make her human again, the answer is probably yes. Being an android has all sorts of pros as well as cons to it. If reverting back into a normal human means losing all those potentially good traits, that's a major change. If Krillin really wanted what was best for 18, then he should have consulted with her and discussed it. In any case, the real reason 18 acts all prickly is because she thought Krillin was trying to win her favor, which, as it turns out, she's wasn't averse to. The two of them apparently reconciled and now they live happily together. That probably wouldn't change even if 18 were made human.
