Charlie met Mildred in early 1918 at a party at Sam Goldwyn's beach house. Although Charlie later insisted he had no interest in Mildred except for sex, he found himself courting her anyway and eventually she became pregnant. Charlie married her and was willing to make it work although he did not think Mildred was very bright. The pregnancy was a false alarm (if there was a pregnancy at all), but Mildred soon became pregnant again and gave birth in July 1919 to a baby boy who lived only 3 days. Soon after their marriage, Mildred signed a contract with Louis B. Mayer who began billing her as "Mrs. Charlie Chaplin" which, understandably, annoyed Charlie to no end.
The marriage ended in November 1920. Mildred later claimed that if the baby hadn't died she would still be Mrs. Chaplin. Personally, I doubt it would have lasted. Charlie was already feeling trapped & he would not have been faithful. In fact, he already had an affair with Florence Deshon, whom he was in love with and wanted to marry, and later, before the divorce was final, he began a relationship with May Collins.
In January 1927, Mildred wrote a series of articles for the Syracuse Journal in which she describes her life with Charlie. Her version of events is very different than Charlie's, including their first meeting. I will post the article later today.