Mujerón is a augmentative of "mujer" (woman), meaning "a great woman" or "a powerful woman." It's a less common, more emphatic way to describe a woman with strength, confidence, and presence.
In the song, Ivy Queen uses it to assert her dominance and self-worth, warning her rival to "aguante presión de este mujerón" (handle the pressure from this great woman). It perfectly captures the song's theme of female empowerment and resilience.
The song opens on a phone call. Someone has seen her partner with another woman, and before he can start explaining she shuts the conversation down. She does not want the excuses and she is not interested in a jealousy scene.
Instead of waiting with her arms crossed, she does her hair, puts on a short dress and drives to the other woman's address. What she delivers there is not a fight. It is congratulations. She hands the man over as a gift, payment for the suffering he caused, and tells the other woman exactly what she is inheriting. She has already found someone who spoils her, holds her hand and says what he feels.
The title line, "La vida es asi", is a shrug rather than a complaint. That is how life goes: if another woman's leftovers make you happy, they are yours. The closing repetition, "Asi que calmala", tells everyone still making noise about it to calm down. It is a classic Ivy Queen position, a woman setting the terms and walking away on her own schedule.