Garrett began the day with a three-stroke advantage over the chasing pack after a superb 64 yesterday [Thursday], but saw that reduced to just one shot today [Friday] as she carded a 73 to sit at seven under overall.
Only a birdie at the 18th preserved the 28-year-old's lead at the top of the leaderboard ahead of Caroline Masson, Celine Palomar and Florentyna Parker on six under.
"It was probably 100% different to yesterday [Thursday]," Garrett said on ladieseuropeantour.com.
"I fought really hard out there today [Friday] and I suppose that shows a bit of character because it could really have been anything today [Friday].
"My putting saved my life, pretty much, so I'm quite happy with a 73. A little bit different to yesterday [Thursday] but I'll take it."
England's Laura Davies had been poised to take the lead into the third round after reaching eight under par, but a triple-bogey at the last hole saw her drop to five under.