If you're already on depression meds, are you seeing a doctor regularly? Please, talk to your doctor in detail about this and ask the doctor about positive coping mechanisms that help you but don't punish your daughter for her chattiness. Chattiness is perfectly normal for a child her age -- and is probably a very good sign of intelligence and verbal ability too, so as annoying as it can be at times, it's not something to treat like it's bad behavior. She does need to learn some boundaries, like all four-year-olds do, and gently but consistently enforcing a quiet time is a good idea. Do you give her structure for quiet time? She needs to have it at a consistent time each day, in a consistent place, maybe using a timer, and with plenty of good, engaging quiet activities so quiet time is attractive to her and she doesn't get bored and wander out after two minutes.
"Talking to her like she talks to me" until she cries isn't going to help either of you; that works temporarily for you, but in the long run may make her feel like she can't talk to mom when she needs to.
She's at the age when the whole world and every day in it is SO interesting to her and she wants to share it with you -- and share it and share it until you just want some quiet. We've all been there as parents. But you've got older girls and surely at least some of them did this too, so you know it's a phase that will end; is it possible that it's the depression, not her chattiness, that's really at work? Try to focus on carving out some time for yourself without making her feel like she has to clam up. Engage her older sisters in talking and playing with her more (they may not love it but they're old enough to take your instructions to play a simple board game with her while you escape to another room for a while). Or sometimes, have her draw pictures of what she wants to tell you rather than talking--make it a game, get her great crayons to do it, etc. Or get your husband to take over with her for you and let him be her listener. Yep, you get the brunt of it since you're home with her but he can engage her with lots of questions when he is home and on weekends.
And do ensure you are not just getting meds but also talking to your doctor about this -- it sounds like you have a lot on your plate right now.