"She will ask why I don't answer her calls - what should I reply to this?"

Just tell her you were busy. Period. She doesn't need any complicated explanations.

M-43 W-40
2D - 9 and 5

Emotion, yet peace.
Ignorance, yet knowledge.
Passion, yet serenity.
Chaos, yet harmony.
Death, yet a new life.

RECONCILED AND WISER