Let's call this person Alice.
Alice is currently in therapy and taking drugs to treat a long lasting depression. Alice is also quite egocentric i.e. likes to be in everybody's focus and tries to get attention / confirmation from the group. Alice does that by posting lots of pictures of her dog, telling everybody repeatedly about the food she brought to a social gathering (bought, not self-made) and generally likes to talk about much of her own achievements.
In small dosages I think this is fine behavior but she's very much overdoing it. Furthermore she seems to interpret the absence of such affirmation actions from our side as the presence of hostile feelings. There are times, when the group is not in agreement with her, i.e. a political discussion. While everybody else experiences this as an objective and rational discussion, she gets personal after a while and leaves the discussion because "we united against her". This is objectively false but it's the way she perceives it. From a closer friend I've been told, that Alice has a really hard time after this. I presume because she feels unfairly treated.
Under normal circumstances I would just ignore this person and move on. However, there were times where she was much easier and less prone to be hurt and I enjoyed her being around. Given her condition I also feel bad if we would cease social contact with her. However, given the reoccurring nature of these events that she manages to explode a situation after which everybody feels pissed off, I fear that her own actions might eventually lead to the scenario that she very much fears - being excluded for good. I've had a good deal of patience but recently I notice that I'm feeling fed up with the situation. Still, I suppose this is due to her sickness (depression) so ceasing contact with her would feel unfair.
Given that she already is on medication and professional treatment (therapy), how can I make Alice understand that she sometimes behaves inappropriately with us and that it puts a drain on our relationship?