Does UK visitor visa denial affect US visa application?

A friend of mine who wanted to visit her brother in UK upon birth of her brother’s child applied for a visitor visa to UK and got denied. It was her first try to visit abroad and it appears she was a bit careless in preparing the application, thinking her brother’s invitation letter is strong enough (& all her siblings are living abroad), so she didn’t even show her and her family’s financial evidences or family ties back home. This was seen as risk of not returning back by US embassy, and was stated as a reason for denial. On my personal opinion, her chances of getting UK visa would’ve been quite high if she’d prepared the application properly.

She now wants to visit her sister in US again for birth of her sister’s child. Will her refusal to UK visa affect in any way her application for US visitor visa?

Is there a question in US visa application asking “Have you ever applied for visa to any other countries and been rejected?”. What are the implications if she answers “No”. Do US and UK embassies share visa rejection related information? I am told there is no denial or any stamp from UK embassy on her passport.

What’s the best course of action here? Should she say “Yes, and detail her carelessness” or say “No” to avoid unnecessary risks. Thanks for your advice.

The UK visa denial should not have any effect on the US visa approval. If in case asked, it is good to be honest and truthful and yes, make sure to take financial documents this time.