['My coworker was given a great work assignment this morning. It seems like she did nothing to even deserve it. I wish I could get such great assignments!', 'I hate when that happens.  Things always seem to go that way.', "I know it's really frustrating. I don't know what I should do at all."]
All you can do is just keep doing the best job you can and hopefully someone will notice someday.
My coworker got one of the best assignments at work seemingly without even working for it. I wish I could get better assignments like that!