Is it safe to cum inside 5 days after a girl's period?

No: And again no. You may want to consider using protection to avoid adverse consequences.

Safe?: Depends on what you mean by using the word "safe" I am assuming you are referring to being safe from the risk of getting her pregnant, and the answer to that would be no. Also stds (sexually transmitted diseases) will always be an issue. But other than those two broad categories, you would be "safe".

Safe from what ?: Pregnancy has been documented from exposure on any day of a woman's cycle, including during menses. There are statistically more likely days, often called the fertile window, but these are guesses based on the assumption egg release happens only at that time.If you want to avoid pregnancy, cover up.