I think your mother's question is adorable! She must be a really caring person. Sounds as if she is thinking well -- young people will want to get married - but how will they find Sikh partners. I bet it is not easy.
A good question too. Some certainly must meet other Sikhs and marry. Others may have already been married. Some would marry into Punjabi Sikh families. Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=27209Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=27209
Arranged marriages would be a problem in some cases I would think. Because it is not the Western way, and Westerners converting to Sikhism would not have pind, or family associates, in which most marriages are arranged.
So she has me wondering how they do that too.