This might be a stretch but - perhaps Lana could be infertile? It would explain her apparent longing to become a mother, or maybe she's seeing all her friends having babies and she hasn't found that yet.. Or maybe a combination of both.
I also don't think what she posted is "unforgivable" as someone said. She's allowed to not like her mom, and we don't know what happened behind the scenes. A lot of stans dig and dig for personal information on Lana and when she gives us some those same stans don't want it, or have to critique it. I know it was probably comforting to some people who look up to Lana who don't have good relationships with their mothers to see that she doesn't have a great relationship with hers either.