I have a dcg same age and the same problem . Pop tarts with strawberries was the 'healthy ' breakfast . At first I didn't say anything , I have her 2.5 yr sister so I started with her . She had never eaten oatmeal , so I fed her what I fed my own dd . Dcm would send them with every packaged food you could imagine and about 3-4 cookie and crackers fruit roll ups ugh so when my own dd started wanting it ( she had never tried fruit roll ups) I just left her snacks in the backpack and 3 months later she eats pretty much what I'm serving !! She even likes brocoli !!
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Dcm sent 3 fruit for snack today , and I'm still trying to suggest veggies but a vast improvement over all !!!
I'm not sure with your dcg the crying after trying something new seems abit extreme given her age . I think I would put out lunch as planned and let her decide if she would like to eat or not . Maybe the less made of it would be better .