Indeed, it is possible if one wants to do it. Admittedly she had good genetics, but I had a friend in the 90s, 36 years old, who had a kid and a year later you could not tell she’d given birth. She was slightly below her pre-pregnancy weight afterward. And to answer the objection that “she was just wearing flattering clothes,” I took fully nude photos of her (at her request) after she gave birth so I saw exactly what she looked like.
At one point, I asked her how she’d managed to look so amazing after giving birth. She said that it was mainly not ignoring fitness while pregnant, not gaining a huge amount of weight as that advice is 100% incorrect1, and then one should start to get back into exercise as soon as practicable after giving birth. She was back to working out two weeks after having her kid.
Much is possible with the will, and she had the will so she made the way. Can everyone do exactly the same as she did? No. As mentioned, she had very good genetics. That helps. But she was a single mom and not rich and she did it. Which means more people could.