What are the entry requirements and visa application considerations for a dual US-Thai citizen studying abroad in Thailand?

I have two fairly simple but rather wordy questions.

1) My girlfriend is a duel US-Thai citizen and we will be studying abroad in Thailand this fall. Our study abroad advisor said some countries would require that she enters on the passport of that respective country (Thailand would make her renew and use her Thai passport). I've never heard of this and certainly haven't heard of it in Thailand, has anybody?

2) On our visa applications in the section that says Length of Stay, will there be any issues if we put the honest answer of 104 days even though the ED visa allows 90 before the renewal? We will obviously get extensions once we're there but will the consulate be reluctant to issue it if I say I'll be there 104 days?

We will be applying via the consulate in Chicago. Any info would be greatly appreciated, I really don't want any problems with our visas because we won't have much time. Thanks so much.