"Mother's" Sacrifice ... Because One Wasn't Enough?

In Hebrews 10, the Bible tells us that Jesus is the perfect sacrifice for our sins.  His sacrifice was so perfect that it needed to be made only once to cover us all, unlike the sacrifices the priests offered on behalf of the people day after day, year after year.

Heb. 10:10,12-14

"By that will we have been sanctified through the offering of the body of Jesus Christ once for all...  But this Man, after He had offered one sacrifice for sins forever, sat down at the right hand of God, from that time waiting till His enemies are made His footstool. For by one offering He has perfected forever those who are being sanctified."

But what does the World Mission Society Church of God say?  They teach that Jesus' sacrifice on the cross was not enough to keep us clean from sin.

This is evidenced in their sermon, "Mother's Love":

All the sacrifices in the Old Testament represent our Father who was sacrificed as an offering for sin about 2,000 years ago―and also our Mother who is sacrificing Herself to seek and save the children with devotional love for them in this age.
God has given His children the regulations of Third Day worship and the seventh-day Sabbath worship from Old Testament times. Through such regulations, Mother has purified our souls by sacrificing Herself, so that we may not be cut off from the community of God.

Maybe they mean "sacrificing" as in "suffering hardships" but not in the same sense as animal sacrifices and the sacrifice of Jesus on the cross?  And maybe this suffering of hardship is to help and teach her "children"?  No.

They quote Numbers 19:1-21 (in the same sermon) about the sacrifice of the heifer, and they continue on to say:

Every sacrifice in the Old Testament symbolizes God's sacrifice. Then, whom does the heifer represent? By whose and what sacrifice are we now cleansed on the third and seventh days?
The heifer was a sacrifice representing our Mother who's come into this earth as the Bride of the Spirit. The Israelites were cleansed through the sacrifice of a heifer. This shows that God's children are purified through the sacrifice of Mother on the third and seventh days.
Our Mother burns Herself, being sacrificed as a sin offering; through the ashes of Mother, represented as the heifer, we are cleaned from all our impurities, from all our transgressions and sins―on the third day and seventh-day Sabbath. How can we imagine and describe in words our Mother's pain, sacrifice and love?

Keep reading and see that they are clearly talking about "Mother" (Zahng Gil-Ja) being sacrificed for the sins of her "children":

Through the fact that our Mother is continually getting sacrificed on the Third and Sabbath days, we must know how many sins we have committed.
Some may simply think that they are forgiven because they believe God. However, we must know there is God's great sacrifice and love beyond description in the forgiveness of our sins. By God's wounds we are healed; the punishment that has brought us peace is upon God. Through such a sacrifice by God, we are forgiven. We should realize the love of our Father and Mother and give thanks to Them through the Third Day and Sabbath worships.
Without putting on Mother's love, none of us can enter the kingdom of heaven; we are expelled from heaven, and we can never enter by ourselves.
By the sacrifice of Mother, we are purified. Mother is pierced for our transgressions. By Her wounds we are healed and at peace.

This is in direct contradiction to Hebrews 10:14.  Here it is again in the NIV:
"For by one sacrifice he has made perfect forever those who are being made holy."

Not only that, but if "Mother is continually getting sacrificed on the Third and Sabbath days" for sins to purify her "children," then she is comparable to the repeated sacrifices offered in the Old Testament.  And what does the Bible say about those?

Hebrews 10:1-2

"The law is only a shadow of the good things that are coming—not the realities themselves. For this reason it can never, by the same sacrifices repeated endlessly year after year, make perfect those who draw near to worship. Otherwise, would they not have stopped being offered? For the worshipers would have been cleansed once for all, and would no longer have felt guilty for their sins."

What kind of "God" has to keep sacrificing herself over and over again?  Hebrews 10 says once is enough.