According to Richards' lawsuit, Sheen, 50, has broken stipulations in the trust he set up for their children – Sam, 11, and Lola, 10. But Sheen's lawyer Marty Singer has said the lawsuit is about nothing more than "money, money, money," previously telling PEOPLE that the actress "has received $660,000 tax free each year for almost 10 years" in child support payments, in addition to $10 million from Sheen stemming from their 2005 divorce.
A source tells PEOPLE "Denise filed a motion to protect the kids' trust."
"Charlie is cutting expenses, and the kids are the first to go to maintain his lifestyle and it's been going on for a very long time," the source tells PEOPLE.
The source continues that Richards has had trouble collecting child support from Sheen, saying it's "like pulling teeth."
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According to Richards' lawsuit, Sheen allegedly sent text messages to Lola in which he disparaged his ex, writing "B---- couldn't act hot in a fire or wet in a pool." Sheen's lawyer previously told PEOPLE those messages were intended for Richards.
"The texts were to Denise," Singer said. "It is very sad that she uses the children to get more money from Charlie and makes it almost impossible for Charlie to see his daughters."
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The source counters this claim, telling PEOPLE, "Charlie knew he was texting them [his daughters] because he often made references to them in the texts."
In the lawsuit, Richards claims Sheen asked her and her children to move into a home next to him he had purchased, promising they would not be evicted should they do so. The lawsuit further claims that in September, Sheen allegedly evicted Richards and her children and has not provided money for them to purchase a new home as his ex claims he had promised to do.
Richards is seeking $1.2 million toward the purchase of a new home for her and the children.
Richards and Sheen began dating after she appeared in his show Spin City in 2001, and they wed the following year. Richards filed for divorce in 2005 while pregnant with Lola.
Richards later adopted a third daughter, Eloise. And in 2013, Richards cared for Sheen's twin sons Bob and Max, whom he shares with Mueller, when Mueller sought help for her drug problems.
In November, Sheen revealed he has been battling HIV after being diagnosed in 2011.
A source told PEOPLE at the time that Richards has known about Sheen's HIV for "a number of years" but that neither she nor their daughters have tested positive.
When he revealed his diagnosis, Sheen said he had paid $10 million to people who knew of his health struggles in order to keep them quiet.
"Denise was one of the few people in Charlie's life who wasn't paid to not talk about his health condition," says the source. "She chose not to because he confided in her. She was one of the few that always had his back and supported him and never expected anything out of it. That's what you do as a human being."