I have a daughter who's about to turn 12 & we began dealing with this same thing last year (among other laziness issues). Like you, it drove me crazy. It might be her room, but its our house - our rules. So when she started Middle School, we created a chore chart on the computer. In large letters on the chart, we added "There will be no reminders given." This has been the toughest part to overcome.
Here's how our chart works (I created it in Excel). We list specific chores, how often their supposed to be completed (daily, every weekend, etc.) & open blocks for each day in the month. She has the ability to earn so many dollars per month doing these specific chores. She gets check marks for completions, x's for missed chores and n/a's where they apply. For each missed chore, she loses $1.00. The chart also has "extra credit" chores so she has the ability to earn back any lost dollars. She gets paid at the end of the month based on the completed chores.
Here's the other kicker - things she wants but doesn't need, she has to pay for with her own money. She wants a new cell phone & its something she's been saving for for several months now. That's her motivation for earning the money.
Something we haven't done yet, but we're going to start is to make her take a portion of her monthly allowance and deposit it into her savings account. Even if it's $5.00 per month, she'll get to see her money at work and earning some interest (even if it's small).
Some people might find this tough for an 11/12 yr. old, but let's face it, life's tough. Things in life aren't handed to you - you have to earn them. The sooner they learn the way life really is, the better they'll be prepared for adulthood. It's worked for us so far & I hope this advice has helped you in some way.