Agree with kpopp above to a certain extent however... I see your catch 22 and I would do neither... you cant not respond because thats what got you in this position in the first place... you dont want tit for tat... but you cant look desperate either or youre done for... so I would casually reply... do not repeat do not directly reply to the message she sent you and go overboard telling about we're just friend or dont worry about this or that... you are not in a relationship at this time and quite frankly it's none of her business and then you leave room for imagination... so if you reply I would be as nice.. friendly... confident... as possible... Something along the lines of... Hey sorry I haven't said hello lately but I've been busy... ya I have a few new friends... I hope your doing well I think of you and miss you from time to time... maybe we can get together for coffee sometime and play catch up...