well if you know it's no good, (which it isn't) you should let her know, it's not of the Most High for her to be dealing in that. The hard part is trying to break it down to her, does she believe in the bible? if so you can show her where it states once we die we know nothing, so it's no way for a medium to be speaking to her father & you can also show her the example of how a servant of the LORD was trying to summon the dead since the LORD stop providing him with answers to his questions & the servant thought they were speaking to the dead personbut in end he was really speaking to satan. But if you don't say anything to her, then her blood may fall back on your hands....
Ezekiel 3:17-21 (King James Version)
17Son of man, I have made thee a watchman unto the house of Israel: (therefore hear the word at my mouth, and give them warning from me.)
18(When I say unto the wicked, Thou shalt surely die; and thou givest him not warning, nor speakest to warn the wicked from his wicked way, to save his life; the same wicked man shall die in his iniquity; but his blood will I require at thine hand. )
19(Yet if thou warn the wicked, and he turn not from his wickedness, nor from his wicked way, he shall die in his iniquity; but thou hast delivered thy soul. )
20Again, When a righteous man doth turn from his righteousness, and commit iniquity, and I lay a stumbling-block before him, he shall die: because thou hast not given him warning, he shall die in his sin, and his righteousness which he hath done shall not be remembered; but his blood will I require at thine hand.
21Nevertheless if thou warn the righteous man, that the righteous sin not, and he doth not sin, he shall surely live, because he is warned; also thou hast delivered thy soul.