All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is due on the woman mentioned in the question to hasten to perform the obligatory Hajj if she has not done it yet as long as she is able to do it because Hajj is due immediately on the one who has the financial capability and is able to do it. She should not give priority to helping her son get married over performing Hajj, because Hajj is due on her, whereas helping her son to marry is not due on her.
Allaah Knows best.