Cristina has been a fan of Let's Plays since The Sims 1; she used to talk to herself while playing The Sims and pretend that there was an audience. She has also said that her favorite Let's Player was HeadbuttArcade (now AndrewArcade), whose videos she would watch even on the way to school when she was younger. However, she was shocked to find out when Andrew closed his channel, without warning, and resolved to start a channel of her own. Lifesimmer has since become the most subscribed Sims Let's Player with nearly 800,000 subscribers on her main channel.
Cristina, at age 13, created her channel on May 31 2011. As explained in her now unlisted YouTube Story video, the name "Lifesimmer" is a portmanteau of "Simmer for life". Lifesimmer's first ever series was a Let's Play of the newest Sims Expansion Pack - The Sims 3: Generations. This Let's Play focused in on the lives of Zack and Lara Baker and their many kids; one of whom was named in Andrew's honor. Lifesimmer later referred to the series as "bad" and "embarrassing", hence her decision to private and later remake the entire Let's Play.
Lifesimmer began her rise to prominence in 2012 with her The Sims 3: Supernatural and The Sims 3: Seasons Let's Plays, both of which have received over a million views for her channel. Lifesimmer would then go on to release the remake of her first ever Let's Play, The Sims 3: Generations, in 2013. This series earned over two million views just for its first part, making it her most popular Let's Play to date.
Lifesimmer began to upload more infrequently throughout the first few months of 2016. She addressed this as a consequence of having moved out, and needing time to adjust, however fans began to worry after several months passed and she did not return to YouTube or social media. It is now known that Cristina and Mark began to date circa June of that year.
Lifesimmer released her The Sims 4: Vampires overview in January 2017. The video description mentioned her struggle with motivation and other mental health issues, such as anxiety, and that she was on her way to recovering and making content again. As of March 2017, she had still not released new content, but mentioned on a Twitch stream with Mark that she was working towards it.