@Seadad
It's not about blame - *@aSofaNearYou* - and OP has not been berated - but it has been pointed out by me and others that she doesn't fully appreciate the harm she caused. It's about recognising that the relationship went wrong when one person was an ADULT and the other was a CHILD.
You should reflect on who has the power, who has the maturity and who has the responsibility in a Child/Parent relationship. OP wasn't 'awful' and I sympathise with her circumstances- but she absolutely did the wrong thing in avoiding any meaningful relationship with a child she was a step mother to. She has said she was indifferent and she didn't persevere with the things that matter - trust, affection, interest , support, engagement, understanding. All that parent stuff! Children can be difficult- it doesn't make walking away OK. You can't objectively say it's OK as a step parent to opt out - while giving such things to other children in the same household. Anyone can understand how and why - but it's not OK.
We are reading a totally different thread. From what OP has said she did not avoid a meaningful relationship with her, she tried hard to forge one, did a great deal for her, and it was firmly rejected at each point. OP feels she always did include her, and tried with her, but the avoidance and ignoring came from SD, not her. I would love for you to quote me where OP has apparently gone out of her way to avoid a relationship with her. I see no evidence that OP did not act in a mature way, or actively caused any harm. The SD may FEEL harm, but it wasn't actually caused by OP from her account here.
I can absolutely 100% say it is acceptable for a SP to withdraw. In the face of the SC being openly hostile and ignoring them this is not only the only thing they can do (again, what was she supposed to do, follow her around until she spoke to her? Can anybody answer that queation?), but it is also recommended for the sake of the child not only a great deal on this forum, but also by the sounds of things by professionals. "They want a relationship with their parent, give them that space, don't overstep" are all common, firm messages sent to step parents whose step children make it clear they don't want them around.
It's been conveniently glossed over that SD also stole from OP habitually. So this child was openly hostile to her, continuously ignored her, stole from her, and OP continued to do school lifts, make efforts to include her in all aspects of her wedding, made a conscious effort to ensure the children she had with their father did not take up any of his time with her, overburdening herself in the process, and generally spent years mulling over this issue and feeling deeply concerned by it. And yet I'm supposed to objectively deduce that she was indifferent and immature? I think that's absolutely farcical!