Im going to assume you're a woman. Im also going to assume your from indian/pakistani/middle east asian type of family, most likely muslim am i right?
There are still a lot of uniersities you can apply to and get into, i'm pretty sure. I would have hated going to cambridge/oxford, i would not have fit in and the workload would have been far too high. I dont care how great the job prospects would have been after, there are more important things in life.
Go to a university you really want to go to. Do what you really want to do. If you get a good grade in mathematics you will be able to get into a lot of good universities as it is regarded one of the strongest subjects for science/technical degrees.
Also, a little unrelated, but dont get yourself put into a forced marriage if you really dont want it. Finally, i would really say it is best to go to a uni far away from home. You will gain independence and little space to breath. In addition to this you really get to experience what uni is all about, commuting back and form from uni to home will really dull the experience imo. Uni is a lot more than lectures and doing what your mother is proposing will make it only about lectures.