I doubt people wait until a certain age before looking for a partner. Those who are older/behind their peers in romance more likely did not meet the right person until later or were more mature socially to make connections. Some are less mainstream than others (ethnicity, education, intelligence, religious beliefs et al) so the pool of compatible people is much smaller than for most.
Going way back to the OP’s parental thoughts. OP- note how many did NOT meet their spouse in their undergrad school. Graduate/professional educationmay not be at an Ivy for those few who attend an Ivy for undergrad. Hmm- does having only a bachelor’s degree from an Ivy seem more prestigious than an advanced degree from elsewhere?
Again, OP, do not dismiss those Ivy league sports schools but hopefully your mother can learn that they are not superior to all other schools despite any reputation. Go for the best fit for your academic ability and interests plus the many other factors. The atmosphere of the Ivys is certainly not for all of us. Plus they do not represent the top students as there are many better students who go elsewhere.