8. Duchess, it's me. He's bringing her. And for the record, whatever you're planning with Nate, my bedroom floor is off-limits.

for the record: 一种用法是“必须指出，让我提醒你”，就是这句话里的含义。另外一个用法就是按照它的字面解释“正式记录在案，有记录可查的”。还有一个词组也很常用，就是off the record, 解释为“秘密的，不被记录的”，比如警察要盘问线人套资料，他跟线人说“你说的话不会纪录在案，不会被追究责任”，那么就可以说It’s off the record.
off-limits:禁止进入的，禁止接触的

9. -Making sure you're okay. I tried calling, but-
-Oh, yeah. My phone died. Sorry.

手机没电：My phone died. 没电也可以说dead battery.

10. - Uh, you still positive you don't want me tagging along?
- Yeah. No offense, Dad, but I think you, me and Serena--Things are awkward enough.
- Well, tt's not like I'd have to be a third wheel. I can bring a date.

positive相当于sure, tag along尾随，跟随
No offense: 无意冒犯。当你要说一些比较直接但又是事实的话（比如说对方很boring,或者很胖之类的），就会先说no offense——我无意冒犯，不过我们就事论事的说……
third wheel: 就是第三者啦