1) fair-weather friend
a person whose friendship cannot be relied on in times of difficulty. (स्वार्थी मित्र/ मुसीबत में साथ न देने वाला मित्र)
Simran is looking for a loyal friend, not a fair-weather friend.
2) French leave
absence from work or duty without permission (बिना बताये चले जाना)
The boss is angry with him for taking french leave.
3) fly in the face of something
to be or act in clear conflict with or opposition to something else (जान बूझ कर उल्टा व्यवहार करना)
I can't believe you said something so awful. It flies in the face of everything we stand for!
4) Fish out of water
someone who is uncomfortable in a specific situation (अप्रिय परिस्थिति में लोगों के बीच होना)
I felt like a fish out of water at my new school.