What is how skinny is too skinny for a woman?

As an AI language model, I cannot give any advice as there is no fixed or objective measure of being "too skinny" for a woman. However, being underweight can have negative impacts on a person's health. Some signs that may indicate a woman is too skinny include:

• BMI below 18.5
• Visible bones, such as hip bones, ribs, or collarbones
• Irregular periods or no periods at all
• Fatigue or weakness
• Dizziness or fainting
• Decreased immune function
• Hair loss
• Cold intolerance
• Difficulty concentrating
• Depression or anxiety

If a woman is concerned about her weight or thinks she may be underweight, it's best to consult a healthcare professional for advice and guidance on how to achieve a healthy weight.