Manning, a former army intelligence analyst, posted a picture of herself on social media with short blonde hair, lipstick and mascara, wearing a V-neck navy blue top with white trim.
The photo replaced an old Twitter profile picture that had shown Manning in her previous incarnation as Bradley Manning, a male soldier in military uniform and beret.
On her release from Fort Leavenworth's all-male prison on Wednesday, Manning had vowed to put her previous life behind her and said she was "excited" about the future.
Her social media posts immediately after her release showed people clinking champagne glasses with the caption, "Here's to a new beginning."
Another post showed a single slice of pepperoni pizza on a plate, with the words "So, I'm already enjoying my first hot, greasy pizza," followed by a smiley-face emoticon.
Manning was sentenced to 35 years in prison in 2013 for leaking more than 700,000 classified documents to WikiLeaks three years earlier.
She served seven years, and twice tried to take her own life last year alone, before then-president Barack Obama commuted her sentence just days before he left office in January.
In a statement to ABC news, Manning said: "As I rebuild my life, I remind myself not to relive the past. The past will always affect me and I will keep that in mind while remembering that how it played out is only my starting point, not my final destination."
