i have two good friends who pretty much fit that category. i basically had to go off on them before i could make them see i was needing them at that time. (i really don't recommend that tactic). eventually i was able to set some boundaries for our conversations.when i REALLY was in need of support i had a "key word" which i would use to make them aware that i needed all their attention to help me through what i was going through at that time. it did not trivialize their problems or make them seem less significant, but it did help our friendship to know the boundaries were there.any real friend will not force themselves or their troubles upon you in your time of need. hope this helps.

alikat