No doubt she was sincere, but God never meant for anything to be used as a good luck charm - especially a cross. Thinking that a charm or other object will bring us "good luck" is based on superstition - which the Bible strongly rejects. The Bible says, "This is what the Sovereign Lord says: I am against your magic charms with which you ensnare people" (Ezekiel 13:20).
Never forget what a cross stands for: the death of Jesus Christ, the Son of God. He was innocent of any wrongdoing, but His enemies still put Him to death - a death of almost unimaginable pain. The Bible says, "His appearance was ... disfigured beyond that of any man and his form marred beyond human likeness" (Isaiah 52:14). But Christ's suffering on the cross went far beyond His physical pain - for on the cross all our sins were placed on Him, and He suffered the death and Hell we deserve.
The cross should also remind us that we belong to Christ, if we have truly committed our lives to Him. Because He died for us, we can now be part of His family forever. The Bible says, "How great is the love the Father has lavished on us, that we should be called children of God! And that is what we are!" (1 John 3:1).
Do you know for sure that Jesus Christ died for you, and that someday you will go to be with Him forever? If not, open your heart to Christ and commit your life to Him without delay.