The Dutch golfer turned in only 39, but then had four birdies in a row from the 11th and finished with a level par 73.
That kept her on three under par, where she was joined by Finn Ursula Wikstrom, whose 70 included two bogey sixes, but also five birdies.
They are a stroke ahead of Wikstrom's compatriot Minea Blomqvist, who had her second successive 72.
Swede Pernilla Lindberg, one of five first round pacesetters, holed-in-one with a seven-iron at the 147-yard 11th and then birdied the 14th and 15th, but in the end had to settle for a 75.
It dropped her into a tie for fourth with her fellow countrywoman Louise Larsson, Italian Diana Luna and also English amateur Charley Hull, playing her first European Ladies Tour event.
Hull is the 16-year-old from Woburn originally dropped from consideration for next month's Curtis Cup after deciding to go to America and play in her first major championship, but then named in the team.
Boeljon missed a two-foot putt on the last and said: "It was a shame, but overall I came back good and I'll take the confidence I had on the back nine through to tomorrow [Saturday]."
Wikstrom said: "If you trust your swing you can fire at the pins. I had some more chances, but it's much better."