Amanda Bynes insists ... she's not having a Britney Spears-type meltdown -- telling friends she does NOT need a conservatorship because she's perfectly capable of making her own life choices.

Amanda is adamant ... she has no substance abuse problems and she dismisses the pending criminal hit-and-run charges and the DUI cases -- claiming the charges are all bogus.

Amanda says her family has NEVER brought up even the possibility of a conservatorship. This is consistent with a contact TMZ had with a rep for Amanda's family several months back ... the rep insisted the family felt Amanda had NO mental problems.

We do know several friends and relatives of Amanda's family have tried convincing them Amanda needs professional help, but as of early summer the pleas fell on deaf ears.

As we first reported -- Amanda's neighbors and fellow gymgoers have become increasingly alarmed ... claiming Amanda has shown worrisome signs of mental distress, including speaking to inanimate objects.

As for reports Amanda's entering rehab in the next couple days – the actress says no way ... there's no reason to check into a treatment facility..