It says in the Gemara of Baba Mesiah (75b), that Rab Dimi said that if someone lent a "Maneh" to his neighbor and knows that he has nothing to repay him with, the lender may not even pass in front of the borrower. The reason is that we do not want him to embarrass the borrower.
It is asked in Dibrei Mordekhai, that if a person lends a neighbor, in the same building, some money and the time for repayment has passed without being paid back, may he pass him on the stairs, or in a meeting of the tenants and so on? The answer is that if the lender knows that the borrower is unable to repay his loan, he may not ask him for the money.
It is also forbidden to pass in front of him, so that the borrower does not feel that he has come to claim his money. However, if the lender meets the borrower on a regular basis, and also if he does not know that the borrower does not have the money to repay, then he is permitted to meet him and speak with him, because the borrower will not be embarrassed.
(See Dibrei Mordekhai, Parashath Mishpatim, Halakha BaParasha)
Dinei Mamonos, Dinei Mamonot, Dinei Mamonoth, meeting one who cannot repay