Step parenting is not an easy task by any stretch of the imagination. By marrying a man with children from a previous marriage, you assume the responsibility for being a part of those children's lives and caretaking, this usually comes usually with a bias (even if it's small) against you, the Stepparent. You have to learn to live with and discipline children that aren't yours, children that may not give you the time of day, much less validate your discipline attempts. Children with psychological issues are an entirely different subject and are usually influenced by a mentally ill parent!
And if that wasn't difficult enough, then there's the Ex, regardless of if she's crazy or Psycho, one way or another, this woman usually causes stress in your life, even if she's not a Bitter Ex. The Ex will never go away as long as you are married to your husband and they have children still at home to raise, so you're going to be dealing with this woman for a very long time.
The Bitter Ex is a whole other ball game and I pray for you if you’re dealing with a bitter, crazy or psycho ex wife. The Bitter Ex is a woman who is vindictive, hostile, irate, often irrational (sometimes she is so blinded by her hatred for you and your husband that it is even to the detriment of her own children), and she can be violent. She is often so blinded by her own anger that this woman will go to any length to make your lives a living hell. More often than not this stems from her uncontrollable jealousy...either jealousy over you because she still loves him, or she is missing her old life where the family was a "solid unit", your living in the family house, she's lost her jobs, houses, cars, money and boyfriends etc...the reasons are numerous.
So not only do you, the Stepparent, have to deal with kids that aren't yours, you now must find a way to deal with The Bitter Ex. From experience, I offer the following advice that may help:
1. Above all, NEVER lose your temper. The Ex will go out of her way to try to irritate you, and getting you to lose your composure is her goal. Bite that tongue and save those come-backs for your husband behind closed doors. Always keeping face will not only irritate her more (which is excellent "revenge" in itself, if you feel the need for it), but will give her no reason whatsoever to badmouth you in the future, trust me the people in the community know what and who she is anyway. And the children will see that she's the one who is irrational, badmouths you etc. and will eventually call her out on it, maybe not until they are grown and out of the house, but they see what she's done.
2. Always attempt to create a harmonious relationship between everyone. Try to be that peacekeeper. No, you don't have to be her friend, but by being civil and keeping the door open for communication can do wonders for helping the kids, which should be everyone's main concern...even if she is so blinded by hatred and jealousy that it doesn't seem to be hers at the moment.
3. If his Ex is really teetering on the edge of being a Psycho Ex, it would be in your best interest to protect yourself by documenting everything! You never know if you may need documentation later for restraining orders. Keep all letters, emails and voicemails from her that may prove her unstable state of mind later down the road.
4. Try to detach from the Ex situation and let your Husband deal with her. After all, she's really not YOUR problem, it's his. Detachment may save your sanity.
5. Never badmouth or say anything negative about the Ex in front of the children. This will only alienate the kids from you as they feel an innate need to defend their mother, even if she is psychotic.
6. Find a support group for stepparents, whether it's online or in your community. There are lots of online resources for stepparents & the unique issues involved.
7. Try not to take things personally, even if it's an attack intentionally aimed at you. His Ex is bitter for a reason, if she's so vindictive that she has harmed and alienated her own children that is something that SHE has to work out for herself. Her attacks at you stem from some miserable insecurity within herself, if she was the one that left the marriage bed she is probably filled with remorse or regret every time she see's you and your husband out having a great time and in love. Remind yourself of this, and don't take it personally because she has a mental condition. Pray for her and let it roll off your back because if she's psycho hopefully she'll eventually be ordered into a psychiatric evaluation if she's harming her own children.
8. Relax! And hang in there. It really is worth it in the end, those kids grow up and leave and so will their mom.