... the first gloomy suspicion that the warning, after all, might have some weight to it."

[KuaiLe]

I read this from Wedlock Edge, a short story by Canadian Writer Alice Munro.

The narrator got a job in her college's cafeteria and her housemates said “Boys won’t ask you out if they see you at a job like that.”
And the narrator said to them "I would not want to go out with anybody who would make such a judgment."
Then the narrator told her uncle about this conversation with her housemates.
Upon hearing that, her uncle said "Absolutely right. That is absolutely the attitude to take. Honest work. Never listen to anybody who wants to put you down for doing honest work. Just go right ahead and ignore them. Keep your pride. Anybody that doesn’t like it, you tell them they can lump it.”

Then the narrator narrated:
"This speech of his, the righteousness and approval lighting his large face, the jerky enthusiasm of his movements, roused the first doubts in me, the first gloomy suspicion that the warning, after all, might have some weight to it."

I'm at a loss about the last bit. Does "the warning" refer to what her uncle said? Like he "warned" her to keep her pride?
And what does "this warning might have some weight to it" mean?
Is the whole paragraph saying that what her uncle said was important and she felt she should listen to him?

 

[5jj]

The warning is the one given by her housemates: “Boys won’t ask you out if they see you at a job like that.” Her uncle's words suggest to the narrator that there might be some substance in the warning. She begins to doubt the truth of her uncle's words.

 

[teechar]

The strong reaction from her uncle to what she had just told him made her think that the warning from her housemates is perhaps not frivolous or incorrect. She started thinking "Perhaps that warning is useful, and I should pay attention to it".