The 'Freaky Friday' star's coach quit her job when she found out that Lohan, 27, had briefly relapsed on her recovery from alcohol addiction, reported Us magazine.
In a recent episode of her reality show, the troubled star confessed to Johnson that she had relapsed and had some wine shortly after completing her court-ordered stay in rehab last year.
Lohan had earlier denied that she broke her sobriety but later she had a change of heart and confessed.
"Being in recovery and leaving a place where you're in this little bubble and everything is safe around you, it's really hard. I jumped right into a relationship where we weren't on the same page. I wasn't considering the fact that the person I was seeing does drink, and I had a glass of wine. I just had so much guilt," she said.
Johnson got frustrated with this behaviour and finally decided to walk away.