I suspect they would say that a person who would do such a thing has never received the blood of Christ and is mistaken in her conversion. I suspect they would say that she does not have nor ever had the mind of Christ and does not have the indwelling Holy Ghost.
If it were possible that she were saved, of which I do not believe she was, but if it were possible and she had been partaker of the Holy Ghost and were to commit such an act with the Holy Ghost indwelling her, that to renew her to repentance again is impossible, seeing she hath put God to an open shame.
Again though, I think they would say that she never was saved to start with.
Matthew 5:16, KJV
16 Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.
John 14:23-24, KJV
23 Jesus answered and said unto him, If a man love me, he will keep my words: and my Father will love him, and we will come unto him, and make our abode with him.
24 He that loveth me not keepeth not my sayings: and the word which ye hear is not mine, but the Father's which sent me.
Romans 6:1-4, KJV
1 What shall we say then? Shall we continue in sin, that grace may abound?
2 God forbid. How shall we, that are dead to sin, live any longer therein?3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death?
4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
Romans 12:1,2, KJV
1 I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, [which is] your reasonable service.
2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what [is] that good, and acceptable, and perfect, will of God.
Ephesians 5:2, KJV
2 And walk in love, as Christ also hath loved us, and hath given himself for us an offering and a sacrifice to God for a sweetsmelling savour.