• Before proposing create an unplanned unusual absence.
  • When you are back after some time her/his reactions are the clue.
  • If they are bothered go for it else wait for some more time and again unplanned absence.

https://hemantpandeyblog.com/2017/09/16/should-i-propose-a-close-friend-who-i-have-been-with-her-about-a-year/