What can my friend do?

She's from France but married US citizen in late 2017 and is a resident. They have a 2 year-old son and the husband has been abusive for the past 4 months.

He doesn't punch her nor leaves bruises but has pulled her by the hair, spat on her, threw juice in her face during an argument and backed her against a wall. She never expected that and wants to leave him. She's afraid of losing her residency and she's wondering what about her child. The kid was born here, not in France. What can she do?
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His excuse is that he doesn't slap nor punch her so therefore isn't that dumb enough to leave bruises but he still does the rest mentioned. In addition, it looks like he's cheating too.
What can my friend do?
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