Bynes responded defensively by tweeting that Courtney is "the ugliest woman I've ever seen".
Love has had public issues with substance abuse in the past as well and commiserates with the plight of Bynes.
The musician told the actress she supports her in this dark time.
"@AmandaBynes @eonline Amanda, I wasn't attacking you love. I've been in your shoes before, wasn't easy. DM me, let's talk. Ignore the haters," Love wrote on Twitter on Tuesday.
"Will you people lay off on giving this girl such grief? Shes a beautiful talented young woman, we all go through our ups and downs. grow up! (sic)."
Over the weekend, Bynes began a Twitter feud with Rihanna.
She told the Barbadian beauty: "@rihanna you look so ugly tryin to be white" before stating she deserved to be assaulted in 2009 by then boyfriend Chris Brown.
Rihanna responded to the nasty comments promptly.
"Ya see what happens when they cancel Intervention?" the singer mused.
- Cover Media