If you tell a 21-year-old girl you're dating, "I can't text while working," will she fall for you more?

To put it briefly, "it depends on the situation."
However, if done properly, there is a good chance of leaving a positive impression.

Because,

• A person who is "focused when busy" can look attractive.

• A man who has "clear boundaries between work and personal life" can give off a mature and reliable image.

• Especially from the perspective of a 21-year-old girl, she might feel a strange charm thinking, "Oh? This person doesn't get swayed by me too much?"

But the point here is 'how you say it.'

For example,

• If you just bluntly say, "Don't text me while I'm working," it can come off as cold and create distance.

• Instead, if you say, "I'm really busy when I work, so I can't respond properly. I don't want to give you a half-hearted reply, so I want to talk properly after work,"
  by showing consideration while setting boundaries, the chances of her falling for you actually increase.

In summary,

• Be firm but warm,

• set rules while respecting the other person's tone,
  and this can make you appear much more attractive.

Conclusion
Setting boundaries can actually be a good weapon. But the way you say it determines everything.

Sentences to convey the feeling of "I can't text while working" softly and elegantly to a girl you're dating

Soft and considerate style
"I'm a bit scattered when I work, so please understand if my replies are slow. I'll contact you right after I'm done."

A slightly thrilling style
"I don't want to give you a half-hearted reply. I want to talk to you with focus, so let's chat slowly after work."

A cool and mature vibe
"I tend to immerse myself in work, so I don't check my phone much. But I'll contact you first as soon as I'm done."

Playfully cute
"No texting with me during work hours! That way, we can both have more fun chatting later."