Colton opened up to Becca at the dodgeball group date's afterparty about his brief but romantic past with Tia, who also competed for Arie Luyendyk Jr.'s heart on The Bachelor's 22nd season.
Becca was already feeling "a little anxiety" from the week's first group date, writing in her People blog, "I was over the drama and was really hoping there wouldn't be any more surprises -- but of course I was wrong!"
She explained, "When Colton revealed the truth about his previous relationship with Tia, I was frustrated, shocked and left with a million questions."
Becca and Tia, a physical therapist from Weiner, AR, apparently weren't just acquaintances when filming The Bachelor.
"We were instant friends, bunkmates and she was someone who I could turn to when times were tough," Becca revealed.
"Sharing the stage with Tia when I was announced as Bachelorette was an empowering feeling for all strong women. My relationships with my friends are lifelong, solid and unbreakable."
Becca therefore didn't know how to interpret or digest Colton's confession, and the bachelor feared Becca might immediately end their relationship since she's loyal to her girls.
"My mind raced and I didn't know what to believe or how to handle the situation. Was it true? Why would he lie about something like this? Was Tia aware he was here? How does she feel? Is Tia okay? Is Colton a player? Can I trust him?" Becca questioned.
Colton told Becca he had enjoyed a weekend with Tia but his feelings were not strong enough to pursue a serious commitment.
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"My friendship with Tia (and all the strong, amazing women in my life) mean the world to me. So really, the first thing I wanted to do was send him straight home," Becca admitted in her People blog.
"But the fact of the matter is I was really drawn to Colton for reasons other than just our chemistry and how impressed I was with his charity for Cystic Fibrosis. I felt like there was an invisible pull, something that in my gut told me to not discount our spark."
But Becca decided not to let her "confusing surprise with Colton consume" her thoughts during that afterparty, and so she put her "focus back into the amazing other guys."
Becca did, however, ultimately offer Colton a rose at the season's second Rose Ceremony -- which he gladly accepted -- despite her feelings of hesitation, guilt and concern.
"Going into my second Rose Ceremony, I was overcome with emotion and really questioning if I was cutout to handle what it means to be the Bachelorette," Becca shared.
"I was truly conflicted in the decision to keep Colton and I remember making myself sick over the potential to jeopardize my friendship with Tia. I made the decision to keep him one more week but not feed anymore into our relationship until I was able to speak with Tia."
Fans will find out what happens when Becca, Colton and Tia reunite during a spa-day group date that will air during next week's episode.
"You'll have to wait until next week to see everything unfold and how my relationship with Colton takes an unexpected turn and what this ultimately means for my friendship with Tia," Becca teased.
The Bachelorette's next Season 14 episode will air Monday, June 11 at 8PM ET/PT on ABC.