painting the corners
The act of sending a social media message or an email to an attached person which can be read as either flirting or just friendly, hoping to elicit a reaction.
I caught him painting the corners on Lizzie. Yeah he sent her this weird Facebook message last night.
paint yourself into a corner
To put oneself in a situation with no visible solution or alternative; to get into a mess
You'd paint yourself into a corner by doing that particular thing.