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If she does not see any reason to stop due to health, maybe you could appeal to her sense of whether or not she is really in control of her choice to consume sugar. There is some evidence out there that sugar is very addictive: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2235907/
Unless she lives under a rock, she knows it’s not healthy, she just doesn’t care. And she is an adult and can make her own decisions.
Trying to change her and control her behavior to match what you want is controlling.
If being with someone who values health is important to you then maybe this isn’t the woman. But it’s not fair to attempt to change her.
Did she ask you for help with this? Sometimes people already know how bad something is, but other circumstances lead them to continue the habit. I am guessing if you’ve already mentioned that sugar is bad to her then she already knows. Maybe just leave her alone and let her come to terms on this on her own. It is not a partners job to try to change their partners habits that they are unhappy with. People can only change themselves. Personally, if my partner didn’t like something I was doing and then handed me a bunch of articles on why it’s bad, rather than asking me how i feel and having open dialogue and leaving me to make my own decisions I would be unhappy with that.