Today, my colleague was in a bad mood and just wanted to do tasks like clearing drawers and not interact with the children. She was frustrated with a DC crying and said 'right, this is what we're going to do' and she forcefully grabbed her by the hand and marched her over, plonked her hard down on the floor and then chucked her doll that she had brought in from home down on the ground next to her really hard. A bit later on, she aggressively marched over to the same DC with a angry look on her face and forcefully removed her dummy from her mouth. Whilst having dinner, the same DC was trying to take food from another's plate and she again grabbed her hand away in not a nice way and shouted NO. I don't do nappies as I am lunch cover so I let her know that this DC had soiled their nappy, as she was on nappies and there was no other staff present. She gave a look of disgust to the DC and didn't say anything. I made a note of these things. I was looking for advice as I know I need to report this but this member of staff has been there a long time whereas I haven't and I have a feeling I won't be believed as I think she is seen as a very competent member of staff but this was witnessed by just me. How can I approach this please