Community

I would say have him be initially skittish and worried about other people and new locations, etc. So when he first meets someone he mumbles, eyes cast down, etc.

But if that person tries to befriend him the character very quickly opens up and becomes trusting, etc. This way you can have a sense of being naive, ie; don't trust those even close to you while still showing he understands his throat could be slit, just he can't fathom it coming from someone near to him.

Pelor has Christian Aspects certainly, but usually, towards the modern, pentecostal sects. Mormonism might be a good example too, based on the traditionally strong community involvement.

If you want to go way back though, the best comparison is towards the Egyptian sun god Ra. Pelor gives life, to serf and lord alike, and the best way to honor him is be satisfied with yours, and live it. I think it's reasonable to assume that he isn't calvinist, and your life is your own chance to prove your devotion to good and your fellow man.

I think Pelor has been dominant among humanity for a long time, so one way to get into that is to act like even the humans who worship the raven queen are souls in his service, and their 'new' religion is something that can be 'cured' by properly instilling hope. While most paladins do this a little, you could be utterly convinced that any sizeable group of humans that doesn't worship Pelor is wrong- not Evil, certainly, but in need of your help.

Which might be true- In Greyhawk, The druidic deities have been around longer than anyone else, but Pelor still declares his legitimacy.

It may be that Pelor enjoyed a meteoric rise to popularity in his home region- so he was among the first to have thousands honoring him. Humans also breed faster than most other races, compounding the effect.

And it might be that many of those cultures worshipped the sun, before it had a proper divine sponsor. Pelor's faithful might trace their stewardship of humanity to before their god existed!

My solution would be to help fill the religion out, during gameplay.
Talk about your experiences in the seminary, or what happened when you were living among Avandrian Halflings. Tell the party what your missionaries have learned about a region (doesn't have to be true, but you think it is).

If you use your religion to benefit, by suggesting that you ought to have free stuff or bonuses,
she's going to come down on this hard.

On the other hand, if you portray yourself as a legitimate member of a dynamic organization, most DMs will give you some leeway, and may even become inspired to include some of those elements. By giving her something to expand on, you're encouraging small scale worldbuilding.

Just don't overdo it; Pelor's place in the world is (probably) not the central theme in the campaign.
Keep your expansion efforts limited, and relevant.

Which, I admit, isn't hugely imformative...