How do “alignment” subtypes interact with magic item alignment requirements?

Let’s say we have a LG succubus (who therefore has the chaotic and evil subtypes). A nine lives stealer would be a bad weapon for her, since it bestows negative levels to good wielders, and her alignment is good.

But what about the other way around? Both the chaotic and evil subtypes say that the creature suffers effects according to their “subtype alignment”, so I’d guess a sun blade would also cause her to suffer the effect of a negative level. Using a magic item with alignment-based requirements, however, isn’t covered by the subtype rules.

So as one example, could the LG succubus use an enveloping pit (MiC p.159) in the following way?

If you are lawful evil, lawful neutral, or neutral evil, an enveloping pit functions like a portable hole, except that it is 50 feet deep.

She is lawful, but is she considered evil for this purpose? What about a fiendhelm (MiC p.99), which explicitly requires the user be “evil-aligned”, but lacks any requirements along the law-chaos axis?

I couldn’t find any examples of such an item, but what if she wanted to wield something that only required the user to be “evil”, but didn’t have the world “aligned” attached to that requirement?