"Jennifer and Alex have remained in contact after breaking up and have even seen each other since the split. The two plan to remain friends and are also in business together," adds the source. "Alex understands that Jennifer is single, but felt shocked by [her and Affleck's] quick meetup. At the end of the day, Alex wants Jennifer to be happy, but the way everything has unfolded doesn't sit well with him."
Rodriguez, 45, and Lopez, 51, announced in April that they were were going their separate ways after a two-year engagement and four years of dating. "We have realized we are better as friends and look forward to remaining so," the former couple said in a joint statement at the time. "We will continue to work together and support each other on our shared businesses and projects."
Since then, Lopez has been spotted with Affleck numerous times, first at her home in Los Angeles, and most recently on a trip to Montana over Mother's Day weekend. The two were previously engaged in 2002 and split in 2004, but have remained friendly over the years.
A source tells ET that while Lopez plans to remain close to Rodriguez, as she "usually" does with her exes, people close to Rodriguez "feel things might be different" if the singer's relationship with Affleck develops into something more.
"It's all happened so quick," the source says.
A second source told ET earlier this week that Affleck was the one who began pursuing Lopez. According to the source, things between the two "took more of a flirty turn" in February.
"Ben has always had an affinity for Jennifer and was the one who initially started pursuing her and making an effort to reconnect, romantically speaking," the source said. "He wanted to explore things with her beyond a friendship and they've both really been enjoying spending time together."
"Jen and Ben have remained in contact since their breakup and would see each other from time to time, but as friends," the source continued. "Ben started to pursue Jen and made it clear he wanted more than a friendship. The two have always shared a strong bond and are spending time together to see if there is a spark or it's just two friends finding comfort in one another."
Around the time of their reunion, Affleck praised Lopez in an April interview with InStyle magazine. "I don't know whether people know it or not, but the most impressive thing about her (and that is a long list) was her extraordinary work ethic," he said. "She had this humility coupled with the basic assumption that not only did you have to work incredibly hard to succeed, you had to then push yourself even further."
"I thought I had a good work ethic, but I was completely humbled and blown away by what she was committed to doing day in and day out, the seriousness in which she took her work, the quiet and dedicated way she went about accomplishing her goals, and then how she would go back and redouble her efforts," he continued. "She remains, to this day, the hardest-working person I've come across in this business. She has great talent, but she has also worked very hard for her success, and I'm so happy for her that she seems, at long last, to be getting the credit she deserves."