This one seems like it'd be straightforward. It should combine to Caranfindel, correct? No vowel mutations or lenition?
Follow-up question: Glorfindel is the only attested usage of "findel". Would my new name work as a female name?
On the face of it I'm not sure what else the contact of n + f could plausibly produce apart from nf, but at the same time all attested cases of nf in Sindarin come from the reduction of triconsonantal clusters, so I am a bit hesitant.
A possible alternative would be to shorten caran, similar to what we have in Carnen, Cardolan, and Carcharoth. This way we'd get Carfindel, which I think is more uncontroversial form-wise.
There are also some possible alternatives that you can optionally consider, playing around with some phonological rules that are optional in names: Carfinnel, Cerfinnel, Cerfindel.
And yes, all of these names (including Glorfindel) are not gender-specific, so they could equally be masculine or feminine. If you want it unambiguously feminine, you would need to add a suffix, but this would make it too long and cumbersome I think (maybe something like Cerfinneleth might be borderline acceptable, but I wouldn't recommend it).
Thank you. Technically an NPC is trying to translate a Hwenti elf's name into Sindarin so I could (theoretically) have him just struggle just like you did with a specific form (the elf in question says her name is Tyarnifindle in her native language).