My gf has a son that lives out of state. She has accumulated enough vacation time to literally spend half a year there if she wanted to. She has visited him three times this year so far. Each time she has submitted her vacation time request and has been allowed to go upon request without written confirmation. Between her last trip and this trip, she wrote an employee up at work who is her boss's friend. She put her request in a month ago and booked her flight. Nothing was said for a whole month. The night before her flight she gets a group text from her boss stating that no one is allowed to take off without written confirmation. She text back and asked about her requested time off and she was told that she would have to call in if she wanted to go on her trip still. This is obvious retaliation. Is this legal?