Well, you can’t get more straightforward than “Thou Shalt Not Steal”! So, unless the employer has given his employees permission to take home for their personal use any supplies or materials they happen to find at work, than yes, it is stealing. Consider, for illustrative purposes, what if every employee took home the laundry soap, paper towels, toilet paper, pens, paper, etc. they needed? Obviously, the company does not intend to provide all these things to their employees.
Enid, I don’t believe you are “playing God” by sharing with her that she is sinning and grieving the Holy Spirit, but it is her responsibility to take what you tell her to God and ask Him to search her heart and confirm what you are telling her. The problem, as I see it, is that she only considering returning the items to appease you. She is not convicted of the Holy Spirit, because if she were listening to Him, I believe she would gladly not only confess what she has done to her employer, but return the items and delight in the glory it would bring to God. If there is nothing wrong with what she did, why can’t she just tell the employer? Surely he would understand….
I remember as a new Christian being convicted about things I “stolen” before I got saved. I went back to an employer from years past, and told him that I had used his Federal Express account to ship some personal items (Christmas presents to my family in another state). I told him that I was sorry, that I was now a Christian, realized it was wrong and returned the amount of money I had cost him. To my surprise, this non-Christian man knew exactly what I was talking about, and didn’t protest my restitution at all. There was no question in his mind that I had been wrong to use his account for my personal use and he hadn’t forgotten it either! (In my mind, though, had he not known about it, it would have been no less wrong!) I was able to give him my testimony as well. By the way, that’s just one example. I have experienced several other occurrences of having to make restitution, but I won’t bore you with those details!
By returning the items without her employer’s knowledge, she is missing a tremendous opportunity to allow the Holy Spirit to bring glory to God by her repentance. This can be a powerful tool in His hand to bring about conviction to others. Zacchaeus , when he met the LORD, said, “Behold, Lord, the half of my goods I give to the poor; and if I have taken any thing from any man by false accusation, I restore him fourfold.” When the Holy Sprit convicts, a person will only be concerned with getting right with God, no matter what it takes.
As Lisa pointed out, your friend seems to have a lack of faith in God’s ability to provide for her. This makes her actions understandable, but no less acceptable. In addition, she is also going against her husband’s wishes and hiding it from him as well. 1 John 1:6-7 points out, light reveals, darkness hides. We want to walk in the light, allowing Him to cleanse us from all unrighteousness!