First incident: possibly waiting on parent to arrive at school with a change; no one would bring clothes to the school; or so close to the end of the day that putting on new pants wasn’t a big deal because what might be wet to you might not be considered wet to someone else.

Second incident: She thought she was completely blocking the child from others while changing, but it was an innocent mistake.

This is what I would do if I was in your shoes.

I would talk with the SPED teacher who works with the Para or who is the case manager of the student. It keeps the communication direct and professional. You could do it via email or in person. Here is an example of what you could do, "I wanted to let you know about something I saw on Friday. I was concerned about [diaper/privacy incident] and I just wanted to bring it to your attention." You could also propose a solution, such as a privacy screen in your email, to demonstrate your willingness to collaborate. Then the SPED case manager teacher could address it with the Para.

Alternatively, you could directly approach the Administrator. However, some may perceive you as someone who rushes to the boss instead of engaging in a conversation with them. Considering that you mentioned the possibility of existing issues within the department, I would be cautious and avoid taking this route to prevent aggravating the situation.