Dealing with the craziness of the first child

How do you help your first child out of their regressing when the second baby comes?
Lena was great the first week or so when Lincoln came home. She was.a bit needy but it has just been seeming to continue to escalate.
I read to continue to put her needs first because he won't remember but she might. I've been doing that.
I also read to get her to be part of taking care of him so she feels like she has a new baby too rather than feeling replaced. I've done that as well.
I've taken her on special Lena and mommy trips when my husband has been able to watch our son.
When Lincoln naps, I cuddle her or play with her or find some way to make her feel.like I'm there for her.
I've praised her good behavior and encouraged her regularly. I've tried to help her be a big girl by letting her do things her self, like put herself in her own car seat, and then telling her I'm proud of her...
But even with all that, the truth that I can not give her 100% of my attention still seems to haunt her. And she especially doesn't seem to handle me being with other people very well. It's like her neediness is amplified when she has to share me with even more people...
Needless to say after a month of this, I'm struggling and am having a really hard time figuring out how to help her know I'm still here for her, even when.I'm not able to give her my 100%....
This is me reaching out, anyone else have ideas?