The actress posted a photo of her and Monteith on Twitter Monday, along with a message thanking her followers for "helping me through this time with your enormous love & support."
"Cory will forever be in my heart," Michele wrote.
Monteith was found dead July 13 in Vancouver, British Columbia. An autopsy revealed the 31-year-old actor died of an overdose of heroin and alcohol.
He and Michele played an on-again, off-again couple in the popular Fox series and were an off-screen couple for about a year.