"She's not naive," a pal close to Girardi, 24, tells PEOPLE. "But she was committed to see where this led. She really thought he was a special guy. She was ready to go as far as it could go, and it obviously ran its course."
So when the relationship folded, "it was a shock, to say the least," the source says. "She was really down about it."
And while the split with Pavelka, 32, could actually be a blessing in disguise – "She didn't expect to be married in her early 20s, so it's probably all for the best," the pal says – the breakup was definitely not amicable. "Let's just say they're not going to be hanging out together anytime soon."
Reporting by STEVE HELLING