Avril Lavigne and her fiancé Chad Kroeger announced their engagement this week after a six-month courtship.

While fans of the Canadian rockers used Twitter to share their sentiments, an ex-girlfriend of Kroeger's used social media to express her opinion about the engagement.

Kristen DeWitt expressed disappointment because the rock star had been cheating on her with Lavrigne before the proposal.

"The moment u find out ur ex of four months engaged the girl he was cheating on you with! #classic," she tweeted.

DeWitt sent the message on Tuesday, Aug. 21 the day the couple went public about their upcoming nuptials.

The 27-year-old later retweeted a quote where she may have been referencing her breakup with Chad: "Got played. Got hurt. Cried Tears. Cursed his name. Learned a lesson. Moved on."

DeWitt, who resides in Salem, Ohio reportedly dated Chad until May.

"Chad and Kristen were happily dating until they made a mutual split in May," a source told RadarOnline.com.

"His engagement to Avril completely caught Kristen off guard and the timelines don't match up. Chad had to have been seeing Avril behind Kristen's back."

The source added that that prior to the announcement DeWitt was asked if he was seeing someone else.

"Not to my knowledge the man barely has time to eat during the day. This is the first I've heard of It n we've remained close," she was quoted as saying.

Lavigne and Kroeger told Hello! Canada they had been dating for six months, but according to the source he didn't break up with DeWitt until May.

Kroeger told a radio show in April that he was "dating a girl from Ohio."

Kroeger began dating DeWitt for several years after ending his relationship with Canadian girlfriend Marianne Goriuk in 2002.

The marriage to Lavigne will be Kroeger's first. The issue featuring the Canadian rock musicians arrived on newsstands on Thursday, Aug. 23.

Tags: Avril Lavigne chad kroeger nickelback