very wise indeed

yes, girls don't communicate with words, they communicate with actions - and the words are often diametrically opposed to the actions.  If the actions and words conflict, match both: use words that match the words, and actions that match the actions.  For example if she walks towards your door saying "I'm not coming inside" you might say "You can't come into my home while my wife is away" while opening the door and stepping aside.  

Similarly, you can carry on a friendly conversation with your friend, and throw in some flirtatious (but deniable) actions and words

Trust me you do NOT need to tell her you are interested, she has known all along ...
and if she is interested she WILL initiate

The alcohol thing is an interesting one: it is NOT about manipulating her, lowering her inhibitions, or getting her defenses down ... it is about giving her the excuse that she can PRETEND to be doing something she 'wouldn't normally do'.  

Apropos I saw a very interesting study on social drinking behaviour, where half of a group were given alcoholic beer and half of the group were given non-alcoholic beer, without them knowing which was which.  The people who drank the non-alcoholic beer showed exactly the same "drunk" behaviour as those who were really drinking alcohol ... slurred speech, loss of coordination, lowered inhibitions, etc...

So yes, if she wants to drink, give her drink.  Then wait for her to pretend to be out of control and accessible.  
And you of course also pretend to be getting a bit out of control ... without actually losing control!