At Sorbonne, you cannot study Economics/Management.. it's only for humanities.
For HEC-ESSEC, etc you need to get into classes préparatoires, and as your mother told you, if you fail after 2 years, you fail all the thing (that's why a lot of french students are going to the UK or the USA ^^).
If you wanna study economics, you can get into Science Po. I think the procedure is easier when being an international student, so if you've several citizenships, have a look at which way is easier.