Assuming that a lender sues you and is able to demonstrate that you really did borrow money from them, they will end up with a judgment against you, This judgment will last for ten years, and be renewable thereafter - it's essentially a permanent legal recognition that you owe them the debt. If your mother was a co-signor, then they can also sue her and, if they do, the judgment will be registered against her as well. This judgment will allow them to do the following things:
They can garnish any paychecks that you might earn. A garnishment can take no more than 25% of your (pre-tax) income, and must leave you with no less than $936 per month if you work full-time.
They can garnish money out of your bank accounts. To do this, they must know what bank you work with, and issue them a writ of garnishment. To avoid this, some people constantly shift their accounts between banks. This strategy can slow down collections quite a while, but it's never a permanent solution, because they can also summon you to court to appear for a 'judgment debtor examination,' where you must answer questions about your assets to enable them to garnish. They can also send you written interrogatories, demanding the same information.
If you (or your mother) ever own any real property, they can place a lien on it. This is a recognition that the debt is owed, and it must be paid if the property is sold before the seller gets and profits. If the lien is large enough, they can actually force the sale of that real property.
If you - and your mother - are certain that you'll never own any property beyond these limits of what can't be garnished, then there's little that the debt collectors can do to you. But if you ever want to be able to hold property, you're going to have to pay the debts off, or at least get on a payment plan to do so.
Many people, when confronted with overwhelming debt, can discharge that debt in bankruptcy. Unfortunately, student loans are explicitly not dischargeable under the bankruptcy laws. There is a very limited exception, if you can demonstrate an extreme and unusual hardship that prevents you from being able to repay the debt - not just now, but forever. It is a very, very hard standard to meet. You have to prove something drastic - for example, if you took out loans to be a dancer, and then you had to have a leg amputated - something that severe.
I'm sorry I don't have better answers for you. My heart goes out to you - as someone with some pretty overwhelming student loans myself (almost all new lawyers have this problem). I would suggest you talk to your school's financial aid office first. They may have some kind of repayment or consolidation program you can use. In the meantime, don't communicate with the debt collectors over the phone. They're more likely to say something inappropriate, and it'll be harder to prove it. Try to communicate only in writing. Indicate that you want to repay, but your income is limited, and ask to negotiate a plan. Many lenders would rather be repaid over time than sue and get nothing.