I'm sorry to hear that, blessed. Yes, it is disappointing when you find out someone is caught up in heresy. I try to take heart that the Lord is merciful and only He knows the heart. I do not doubt that there are heretics in heaven; not at all that such beliefs should be encouraged or that submitting to such doctrines is okay, but we really cannot say 100% what God's judgement will be on such heresy. The only thing we do know 100% is that those who deny Jesus will be damned and I understand that to be outright atheism, not being caught up in the wrong doctrine. Like I said though, I do worry about these people's souls. I just can't say in the place of God that they are lost.
I also don't consider much of those denominations to be my brothers and sisters in Jesus. I do make exceptions for 7th Day adventists though--at least I understand that they believe Jesus is God; though, I may be mistaken in that. Basically, anyone who does not acknowledge that Jesus is God I do not consider such people to be Christians and I will not have fellowship with them. Worshipping false idols like Mary, worshipping on the "wrong" day and adhering to the Old Testament dietary laws, and even some on here who really get under my skin with that sinless perfection heresy! Well, they certainly are led astray by the lies of Satan, but I don't know that they are outside the invisible church.
Anyway, I've got to get packed up and leave here. I was on a vacation in NW Georgia for my birthday. It was a lovely time, a great break from work. Now time to head back : ( Well--if I don't work I wouldn't be able to do these vacations, so that's the tradeoff!