When you allow someone, you break all contact. No more emails, txts, phone calls etc. It's appropriate for an ex., someone you're not friends with any more or just anybody who you aren't going to correspond with any more. When the act of allowance is performed, then that person shall become "allowed". At that point you never reply to any messages they send or return any calls. If you go as far as deleting them from your contact list, address book etc. then they shall be known as truly allowed. You can allow a person, an object or an event.
Example 1: I've had enough of Bronwen, she can consider herself allowed.
Example 2: We went to the party but it was DA so we allowed it.
Notice how you don't say you "allowed the party and went home", you just simply allowed it as is the proper context
DA is an abbreviation for the expression "dry as", not meant literally but meaning that something is particularly bad. I believe it derives from someone originally going to a party. We would say a bad party, without much booze to be dry or in this case..."dry as" or indeed "DA".
This should be pronounced as the individual letters, e.g. Dee Ay.
example 1: We went to the party and allowed it because it was DA.
example 2: I went to see that new movie at the cinema but it was DA.