I don't agree that a parent should be taking their child to work if there are other alternatives. Kids get bored and need to have a life of their own. There is plenty of time for time at work when the kid grows up to become an adult. The legal question though is has there been a substantial and material change in circumstance that warrants a modification of your current orders. I'm not sure if this rises to that level but it might. Your instinct that writing to the employer has some merit but keep in mind that causing problems with your ex-spouses employment can come back to bite you later. If your ex loses her job and becomes unemployed how will that impact your daughters living conditions? If you can articulate some reasons you think this situation endangers your child's health, safety or welfare, then I suggest you consult with an attorney in your area to get more information. Good Luck!
It's hard to give much of a response to your question without knowing (a) how old your daughter is; and (b) why you think it's unsafe for her at the pizza place.
A two-year old toddling around a fast-paced food establishment that has been robbed 6 times in the last 3 months is different from a 16-year old reading a book in the manager's office of a place that has never had a crime comitted against it.
Also, from your posting, it sounds like she wanted you to take the child every weekend. If you are not willing to do that, what do you want her to do? And why would you want to interfere with her employment? If she has no child care alternatives, do you just want her to get fired? If she's not employed, are you ready to start paying child support or more child support? Because that is what is likely to happen even if you have a 50:50 deal.
Every case is different and based on the individual facts of the case. Your case may present the facts required to get the order changed and modified so as to be in the best interest of the child. I would be surprised if a judge thought visitation at a pizza parlor is very appropriate or in the child's best interest. Please call and set a free consultation with me at 281-367-4870.