How can I set boundaries over text?

I’ve been parentified by my mom for years. She doesn’t have many friends that I know of so she dumps everything on me. I can shut down her rants to me over the phone by being blunt. But how can I do this over text where she understands I’m done engaging? Today I got a text “I’m gonna rant. No need to reply. This will make me feel better” it’s to a point where I’m disgusted talking to her.