Yours isn't an isolated situation, though, I think a different approach is in order: Understand you're playing a game, and play to not lose. That's right, not to win, which could come back to haunt you, and you're already dealing with one ghost from your past.
When you and Shirley meet, document the results (or non-results) of the meeting as neutrally and accurately as you can, send the documentation to Shirley for review with the instruction, "Please respond by mm/dd/yy or we'll consider this version to be final," and note whatever comments and suggestions she provides in the official project folder for posterity. It's doubtful she'll publish anything that would put her in a negative light, and your providing a reasonable deadline doesn't give her the "I never agreed to this" escape hatch, so this approach boxes her in a bit.
To the extent you can, couple this tactic with a game of ping-pong, by which I mean doing what you can to keep the ball on her side of the table.
You might, for example, establish that the two of you will alternate scheduling and hosting your working sessions. When it's your turn, get the session scheduled a quickly as you can, make sure there's a formal agenda, and document the results (see above) promptly.
Now the ball is on her side of the table, and from what you describe, it will stay there quite a while. If too much time goes by, you might send a gentle reminder, but don't push very hard.
The point of all this? Your assignment is hopeless. It isn't going to happen, no matter what you do, because while you're ready to tango, Shirley has no interest in dancing, and she's embedded in a business culture that supports her in this.
What you're going to do is make sure your hands are clean, while periodically showing your manager the documentation that clearly demonstrates you aren't the cause of the delay so that he can back you up when the time comes. You're then free to spend the bulk of your time and energy excelling at your real job, because that's what you'll be evaluated on at the end of the year.
This story, "Building bridges after a company acquisition," was originally published at InfoWorld.com. Read more of Bob Lewis's Advice Line blog on InfoWorld.com. For the latest business technology news, follow InfoWorld.com on Twitter.