Louis’s main “coping” mechanisms come in two types:
1) The paying someone to sit in a room and talk with him—actually, mostly to listen to him—in an attempt at a kind of pseudo-therapy. For this, he chooses people that are convenient, non-judgemental, and who he genuinely likes—Miss Lily, and Daniel (well, older Daniel is not non-judgemental anymore, but regardless, Louis needed him in order to revisit and reappraise their first interview).
2) Then, there’s the “replacements”—stemming from his loss of and yearning for family, and in which he projects people onto other, newer people. At this point it’s been a straight generational line—Paul and Grace begat Claudia begat Regina. While in Claudia’s case, she was also a stand-in for the child(ren) “of [his] own” Louis couldn’t biologically or legally have, being both gay and undead; as well as for companionship whenever he was (physically or emotionally) estranged from (or just annoyed with) Lestat. Really, she was a lot of roles and symbols to him, which is why he became so emotionally dependent on her (‘my daughter was my sister was my throw pillow…’) and they became so enmeshed.
