license vs seniority

Is there an unwritten rule somewhere where a new hire that is a graduate nurse, needing to take boards yet for RN, gets the open hours over someone who is just an LPN and would have seniority over this other person?

Reason I ask is that I am the LPN. I have been working both day shift AND night shift because there were not straight day shifts open. But now I was told by other staff members that a former employee that worked at this facility as a CNA was hired and will be getting all the day hours!

I'm frustrated because I have been working both shifts since September and have been picking up an extra shift every pay period. We have had someone who just put her 2 week notice in and is going casual, and she had all day shifts. All of the day shifts are med shifts, which is what I have been doing but I also do charge on 2 of my night shifts.

I currently work 3 night shifts and 4 day shifts. I would really like to get off of the night shifts because they are so hard on my physically. Like this weekend, I worked last night (6p-6a) and have to go back tomorrow morning at 6a. I am the only nurse in the whole facility that does that.

I guess what I'm really asking is, do I have a snow ball's chance in hell to get the straight day shifts?

Thanks in advance for your opinions.