All of what follows is my personal opinion, of course. I have held several positions that involved selling to executives and I think my corporate political skills are reasonably good.

It sounds like you have tried several times to have your current manager resolve your issues and she won't; she won't even acknowledge them, so you have no choice but to escalate. It is very risky to do so, however. I've done so, and I've known many others who have done so, and the sr. manager nearly always aligns with the manager. That isn't what you want to hear, I realize.

I think there are a few things you need to have straight:

1. What, exactly, do you propose as an acceptable outcome? You need to know what you want before you have this meeting. You also need to have given your current manager a chance to provide that (more on that later).

2. You need to have documented how you have attempted to accomplish your desired outcome with your manager. You need to establish that you are going to the sr. manager as a last resort.

3. Are you willing to lose your job if this goes badly? Most likely, the sr. manager won't make a decision because [s]he'll want to "empower" his subordinate. At the very least, the sr. manager will go talk to the manager to get her side of the story.

Point #3 brings me to my last point: you don't want to surprise your manager with this. Take one last run at your manager and lay out point #1. Dont' focus on your issues with your job, focus on exactly what you want to happen to be happy in your job. Ask one last time for your manager to resolve the situation. Explain that these issues are critical to you and that you can't continue in this situation. Politely say that if she can't help you, you intend to take the matter up with her manager. Don't be threatening about this. Your intention is to make sure she isn't blindsided about your meeting with her boss.

I can guarantee that your manager's boss will talk to her after your "skip-level meeting". If it surprises her, she will be extremely defensive. The risk in telling her is that it will give her time to think up a response to her boss, but the risks associated with surprising her with it are much worse. Even if things work out better for you, you will have made an enemy out of your manager. That might be unavoidable, but I think you should give her one last chance to make it right and tell her what you're going to do.

FWIW,
Jim