When an ancient Egyptian artifact arrives at a local museum and staff members begin to get murdered one by one, a security guard who is dissatisfied with her job must solve the murders and catch the killer before she becomes the next victim.

The security guard is your main character so they need to come sooner in the logline. Usually you want to be in the 25-30 word area and the main character isn't mentioned until word 21. I'd also find a way to shorten 'who is dissatisfied with her job' into a one or two word description like 'a disenfranchised security guard'.
Is there a reason the security guard has to solve the murders instead of the police? If there is some sort of lock down in the museum that may be worth noting so we know why it's falling to her to figure out.
Maybe.. "When a string of murders at a museum force a lock-down, a disenfranchised security guard steps up to catch the killer before she becomes the next victim."