The 16-year-old was initially omitted from the amateur Curtis Cup team when she opted to skip last week's trial in Nairn, Scotland, after being invited to compete in the year's opening LPGA Major in the United States.
However, the Ladies' Golf Union selection panel reversed its initial policy, which made trial attendance a requirement, and an elated Hull will represent Britain and Ireland against the U.S. in Nairn from June 8-10.
"I'm overwhelmed. I'm so happy, and it should be great," Hull said after relishing her first taste of professional golf in dazzling sunshine at Mission Hills Country Club.
"I didn't think they were going to change it for me, but I'm glad they did. I was upset, obviously, but now I'm really happy that I'm back in the team."
Asked how much she had enjoyed her first round in a professional event, Hull replied: "I birdied my first ever hole of my first ever Major ... so I was pretty chuffed with that.
"I wasn't hitting it very good on the range this morning but I struck it really good out there. I didn't miss any greens, hit my driver really well and I hit my irons pretty close today, so I can't complain about that."
Hull, Britain's top amateur who is ranked seventh in the world, said she planned to maintain her usual tournament strategy this week despite competing against the game's top professionals.
"It's hard to take it all in, but I am just trying to concentrate, not try and do anything different to upset my routine," she added.
Hull ended the opening round at Mission Hills five strokes behind pace-setting South Korean Amy Yang.