An Interesting Comment about Sin

I have been noticing a change in my relationship with my sister over the last couple months. I hope it's a good change... She's been calling more often, a lot really, to say hi and chat and also has gotten back into reading the Bible with me. The World Mission Society Church of God (WMSCOG, or COGWMS, if you'd rather) has somewhat faded into the background. We don't talk about it much at all, which has cut down on the stress, but it's still like a big elephant in the room. We know the disagreement is there and we're just ignoring it for now.

It was our project last summer to read through the Bible beginning to end. Well, the summer got busy and we only made it to about Job. All winter long, she was too busy, so I waited and waited, and now this summer we are back with our reading. It's been nice to be reading the same book and be able to talk about the interesting things we find in God's Holy Book... and we've made a point not to debate about it, just to see what's there.

I was recently talking with my sister after we had each read through the book of Ecclesiastes. And we had a short exchange about a couple verses which I thought revealed something about the WMSCOG view of sin.

We noticed Eccl. 7:20 which says,
For there is not a just man on earth who does good
      And does not sin.
This is not the only verse which tell us there is no one without sin. (If our salvation was based on what we do, how well we obey God, well, we would ALL fail and be lost. That's why we must be saved by our faith in what God has done for us--paying the price Himself for our sin.)

Then we noticed Eccl. 8:5,
He who keeps his command will experience nothing harmful;
      And a wise man’s heart discerns both time and judgment
God's commands were put in place to protect us and help us live a successful life.

After reading these two verses, my sister said...
"So even if we sin, if we are obeying God's command, we will be ok."

Read that again...we can sin and obey God's command at the same time?
How can you sin and obey at the same time?
I think it's because they don't really count ALL of God's commands as necessary for salvation. They say they are ALL necessary, but I think they only focus salvation on the ones that are visible on the outside--attending the feasts, the veil, tithing... Not the ones that are internal, like avoiding lust, hate, worry...

What do you think? Have I got it right?

UPDATE--Yes, I was right.  See "Moral vs. Ceremonial Law."