Does informing a friend for the purpose of encouraging her to help, and presenting the case of a needy family to collect donations, fall under the category of reproach and harm that invalidates charity?

So long as the motive for urging others to donate and informing them of what has been donated is the desire to help the colleague and her brother, and not for reputation, showing off, or reproach, then urging donations is not considered reproach or harm. Rather, it is a righteous deed for which one will be rewarded if done with the intention of drawing closer to Allah.