You are not evil. Stop being hard on yourself with regard to your feelings. My only advice is to focus on your daughter, her well being and your marriage. Try not to compare things with SD and disengage completely. You are civil and don't have any malice towards this child and that's ok.

As for your inlaws don't concern yourself with what they think and feel. They can judge all they want but at the end of the day you don't owe SD anything. It's not your responsibility to make things between your daughter and SD even. That will never happen because of the whole dynamic of the situation. Your only obligation is to your child. The only person that should parent and create a stable life for SD is your H and the BM.

I started to feel like I was less of a "good" person when I had my first baby because I cared so much about him and everyone else in the world all of a sudden mattered much less. That was even before I had a stepkid. But with the stepkid situation that feeling was even stronger and I feel most of the things you listed. 

Oh and also, no you shouldnt have to worry about limiting things for your child to make it even with SDs childhood. Even in nuclear families those things are different depending on income at the time or other factors. And besides, what's the point? Giving your child less wont change SDs past.

I have similar thoughts and feelings- you're not alone! 

You are not alone and you are not evil. These are normal thoughts. I believe that every step parent has these thoughts.

I have exactly the same feeling as u. Have our own daughter who’s a toddler and a super annoying SD who comes once a week. I know it’s not a lot comparing to a lot of step parents here but it definitely feels like forever when she’s around. 

I also don’t want her to interact with DD at all coz I think she is a bad influence. 

I just don’t want her around coz she constantly stares at me and DD when DH is not looking.

i also want DD to grow up to be a better and successful person that she is. 

I never want to plan family “things” involving her. 

A lot of people feel pity for SD. I used to feel bad and really pushed myself to be more involved and engaged. It just become much harder after I have DD and I resent her more and more. 

And you are in good company. We've all had similar thoughts.

And yes, we all knew our spouses/SOs had kids when we met and chose them. But that's not really the issue, right? Similar to most relationships, you don't know what they are like until you are fully in them. Hence the insanely high divorce rate, even amongst first timers.

What we couldn't anticipate before we committed is the degree of dysfunction we would encounter when it came to our partners and their BMs/kids. Often times, we think we can and should work around it, have compassion, not bail when its hard. Except that its extremely hard, and no person other than another seasoned stepparent can really understand that. And then we feel guilty when we are told to work through it, try harder, etc from nonstepparents.

So sure, don't mention to nonstepparents that you wish SD would sometimes disappear, or that you wish you could focus on your nuclear family. It's not realistic, and you will get judged harshly. Save that for us, here, because we can empathize.

However, you can and should push back on anyone who thinks you need to do things like "even out the experiences" for your bio and SD. Redirect them to your DH and BM if they are that concerned. Tell DH that you want to do special things with your LO, even when SD is not there, because LO deserves that. And if he waivers, still do them on your own with LO, because you won't get that time back. And if SD becomes a truly bad influence, then you will need to have some tough conversations with DH about the degree of interaction SD has with LO and any other children you have together. But cross that bridge later.