Advice for a Step Mom
The first thing you need to do it sit down and have a serious discussion with your spouse. You both need to share your expectation and your ideal experience for raising that child together. You both need to set rules and boundaries.
Then your and your spouse should try to sit down and have a talk with the mother of the child. I t may be a very difficult conversation to have but it is one of the most important things you can do for the wellbeing of the child involved.
As a step mom I encourage you to try your best to be friendly to the child's mother. Respect her position as the child's mother. Never talk bad about the child's mother to anyone, especially the child. Try to be the bigger person and just ignore any mistreatment by the child's mother.
Let the child take sometime adjusting to you. Let the child learn your rules and expectations. Understand that some children might feel guilty for liking or loving you because they might feel that is somehow cheating on their own mom. Be consistent but loving with the child. Let the child have a say in what you are called, don't make the child call you mom.
Being a step mom can be a very tough but also a very rewarding experience.
I like the points about respecting the Mother of the child... so important. Always taking the high road and not belittling the child's Mother is essential to keep a healthy and positive relationship. Also valuing joint decisions between just your husband and the child's Mother.. it might be hard to feel a bit left out when they do so.. but if you respect them as the parents, it's the best for the child.