I worked in the two-year-old room in a daycare and many two-year-olds don't catch on to the time-outs until almost 3.
Many young children are single-minded meaning they get it in their head that they want something or want to do something and they just plow forward. They are very "reactive."
The whole reasoning thing sometimes doesn't click until later, and it is then that timeouts work.
If your daughter is LOOKING at you while she does the bad thing, perhaps with a "are you going to stop me?" kind of look then she is doing it on purpose. BUT, it sounds like she's not connecting that whatever she did is a bad thing. And I'm sure she only says she's sorry because she knows that's what she needs to do when she wants out of the time out. You're telling her, but it's just not registering.
With kids like that, you just have to treat them like toddlers and put everything out of their reach and use redirection.
Try timeouts a little bit later, and make sure you have a place of timeout that's really boring. Like the bottom stair. She needs to sit there silently (no singing to herself) and not fiddle or play.
And to know whether or not she "got it" she should not only be able to tell YOU (without repeating after you) what she did wrong, and also what she should do to fix it.
Example: "Why are you in timeout?"
"Because I was touching mommy's glass ornaments"
"What should you do next time?"
"Leave them alone"
"Good job!"