I need a guys point of view! what should i say when i tell my mom i'm moving out?

I'm seventeen and i'm planning on moving out this friday, and my mom already knows i wanna move out, and she's been alot less strict, but i'm still not feeling it and don't wanna stay. I won't have to pay rent cuz i would be staying with my friend chelsea, and really all i'd have to pay for his my cell phone ($20-$60) pecific food. I'd work more hours during the week (my mom said i would only work weekends, which makes sense but really hinders my amount of my income) and i'd be saving up for two months till i turn eighteen. So the usual expenses wouldn't be there, which i'm excited about. And her dad is very relaxed, but not a bad parent ether. ....but the thing is, i don't know how to tell my mom that i've found a place to stay. I had at first gave up on the idea cuz when she found out, she said i couldn't (she's full of ****, i asked the police officer at my school so she couldn't bullshit me, like she tried, which means i was right....) but she kept asking me if i was gonna stay till prom in april, and saying that she's been trying to not provoke me, and to keep me there, which means...i'm guess, that she looked into the matter and found out that i could. But now that i found a place and AM gonna move, she won't bring it up, so I'm seventeen and i'm planning on moving out this friday, and my mom already knows i wanna move out, and she's been alot less strict, but i'm still not feeling it and don't wanna stay. I won't have to pay rent cuz i would be staying with my friend chelsea, and really all i'd have to pay for his my cell phone ($20-$60) pecific food. I'd work more hours during the week (my mom said i would only work weekends, which makes sense but really hinders my amount of my income) and i'd be saving up for two months till i turn eighteen. So the usual expenses wouldn't be there, which i'm excited about. And her dad is very relaxed, but not a bad parent ether. ....but the thing is, i don't know how to tell my mom that i've found a place to stay. I had at first gave up on the idea cuz when she found out, she said i couldn't (she's full of ****, i asked the plice officer at my school so she couldn't bullshit me, like she tried, which means i was right....) but she kept asking me if i was gonna stay till prom in april, and saying that she's been trying to not provoke me, and to keep me there, which means...i'm guess, that she looked into the matter and found out that i could. But now that i found a place and AM gonna move, she won't bring it up, so i don't know how to bring it up without upsetting her...again. It's easier to say "yeah, i'm moving. With my friend chelsea on pickler lake rod. I'm already packing my bags" than to disrupt a perfect good moment with bad news, and saying something awkward like "Hey mom, i'm moving on friday. I'll be with my friend chelsea on pickler lake rd. by the way. Sorry, i know you've been trying to be nicer" What should i say, how can i get her to bring it up??? i can't deal with her getting upset like she did the first time when i told her, even though she was in a pissy mood already..but still, i don't wanna go thru that fight again...help? And don't say "Don't move" cuz i am, and i asked guys specifically, cuz i was hopeing they'd be less emotional and more realistic and upfront...but nice plz...