Does the ability to reflect a Phantasmal Killer spell back on the caster work with any type of telepathic link, or only if you have an inherent telepathy ability or the helm?
A player of mine is asking about using it with Telepathic Bond. I am not sure how they plan to make this work, since Telepathic Bond requires a willing target, but I suspect they will be able to find a way. (My first guess would involve enchantment spells.)
I can see either way applying: you do not have the ability named telepathy, but you do have the ability to communicate telepathically.
Technically by RAW, only the Helm of Telepathy specifically reflects the spell.
Any other option is an ask your GM answer.