I’ve not come across any discussion in a text about her religion (and I looked, a while back). She was from the Quraysh but it’s extremely unlikely she was practicing any kind of idolatry after marrying Muhammad (he hated it, even from his childhood, and never participated in it himself.) But there’s no evidence at all that she was Christian or anything else.
Whereas Waraqah was Christian, as you mentioned. But he died soon after, which makes it pretty impossible that he was any kind of source for Muhammad. Because he was dead, and Muhammad couldn’t read.
And as I’ve mentioned before, nobody can provide any sort of proof at all that Muhammad ever studied from a source, that anyone was teaching him, or he was reading anything about Judaism or Christianity. In 23 years with all his family and friends and followers witnessing revelation, none of them EVER saw him refer to any kind of source.
So the claim that Christians rely on here is unfounded and at best, speculative.