There will be other cars. I'd suggest saving my money so you can show the bank that you have the discipline to save and make payments when the next opportunity arises. Just keep your eyes open for what's out there. Good Luck!
You can now request a copy of your (or your mother can request her's) credit report free of charge. When you get denied credit the credit agencies have to give you a copy for free if you ask.
Check to make sure someone hasn't stolen you or your Mom's identity. If everything on the report checks out - meaning that the reasons the bank cited don't show up, you could go back to the bank and ask them about the discrepancy. Also you could open an account at your local credit union in your own name, and then apply there (possibly with your Mom as a cosigner).
there have been some bills paid late
your debt/ income ratio is too high
credit cards balances are too high
and as it says an account currently over the limit
When a creditor runs your credit report it is not necessarily what your actual balances are to date. If a creditor reports to credit bureaus on the 1st of the month and you paid off that creditor on the 8th and the credit report was ran on the 15th, it would not show up until the next time the creditor reports. Like others have said its wise to obtain a copy of both your mothers and your credit report to fix any problems there might be. You might be able to obtain one for free from the bank that denied the loan. Be patient Its very hard to geta loan at your age, even with a co-signer. Sometimes if you have a savings and or checking account with the bank it will increase your odds in getting approved. Start saving and good luck.