Geremia stated an objective fact about the need to receive the Eucharist at least once a year. But Catholics are also obligated, and it is a mortal sin to violate this, to attend Mass on all Sundays and Holy Days of obligation (like last Wednesday, the Solemnity of the Immaculate Conception). So there are two objective reasons why a person attending Mass after 30 years cannot receive communion.
It's usually a touchy subject and needs to be dealt with, with tact, before everyone in your pew goes up for communion. Most of us Catholics receiving communion are probably guilty of some mortal sin and still receive communion anyway. That does not make it OK. If someone is unaware of a sin or unaware that they've committed a sin, then they have "invincible ignorance" but that's easily changed to "vincible ignorance". Mother-in-laws are good at this.
If this person has received communion, he or she probably has made a confession in the past. Making a general confession before attending Mass is a great way to put yourself right with Jesus. But confessing not attending Mass without resolving to attend Mass in the future would be not really a confession at all. However, there are most likely a great many other things worth confessing in the course of 30 years that would likely steer a heart toward authentic conversion and I can't see how it would be a bad thing.
That being said, the guidelines for receiving communion is a good resource. And those not receiving communion:
are encouraged to express in their hearts a prayerful desire for unity with the Lord Jesus and with one another.
which is nice.