To my knowledge dentists are obligated to give professional advisory.
A few years ago my lower right molar had a large hole in it that required a root canal. My dentist pushed me to have the more expensive procedure to save it rather than to have it pulled.
I went ahead and had a partial root canal done by a dental surgeon who brought to light that this was a particularly difficult situation. In the end, the tooth would have had to be shaved down to a minute amount to fit the crown so again was asked to consider between returning for the rest of the procedure or simply having it pulled.
More for financial reasons than anything else, I opted to have it pulled. Upon seeing the tooth after the partial procedure my dentist actually conceded that he was wrong, pulling it had been the more sensible choice.
He, however at the time had suggested what he thought was professionally less consequential to my oral well being. Cost not considered.
Though he is very kind and on a more recent occasion allowed me to pay the price of the pull and an x-ray of a rotten wisdom tooth alone for the pull and a full x-ray because the single x-ray was more in my price range but he really preferred to do the full.
Ergo, @elbanditoroso I don’t believe saving her money was a valid reason to tell the OPs friend to chew gum to get a broken crown out.
If he wasn’t joking than I say he was unprofessional.