hold/keep (someone) at arm's length

to not allow someone to become too friendly with you.

I always had the feeling she was keeping me at arm's length.

• be fair game
• be falling apart at the seams
• be far and away
• be far and away the best
• be far and away the [best/greatest/worst etc.]
• be far and away the greatest
• be far and away the worst
• be [faster/hotter/thinner etc.] than all get out
• be faster than all get out
• be fed sick to the back teeth
• be fed up to the back teeth
• be few and far between
• be fighting fit
• be fighting for life
• be fighting for your life
• be fighting mad
• be firing on all cylinders
• be first among equals
• be first off the mark
• be first past the post
• be fit to be tied
• be flat broke
• be flesh and blood
• be floating on air
• be flying high