(Mishnah): A widow Mekudeshes to a Kohen Gadol, or a divorcee or Chalutzah Mekudeshes to a regular Kohen may not eat Terumah (even if she is a Bas Kohen, for she is awaiting forbidden Bi'ah);

R. Elazar and R. Shimon permit (even if she is a Bas Yisrael, if the time for Nisu'in came but Nisu'in was not yet done, according to Mishnah Rishonah. Chachamim later decreed that she may not eat until Chupah.)

If they were widowed or divorced from Nisu'in, they are disqualified. If they were widowed or divorced from Eirusin, they are Kesheros.

(Gemara) Question: What is the reason for Rabanan (the first Tana)?

Answer: It says here Havayah ("u'Vas Kohen Ki Sihyeh l'Ish Zar"), and it says there Havayah - "Ki Sihyeh Na'arah... Me'urasah l'Ish." Just like Havayah there is Eirusin, also Havayah here is Eirusin.

Question: What is the reason for R. Lazar and R. Shimon?

Answer: It says here Havayah "u'Vas Kohen Ki Sihyeh l'Ish Zar", and it says there Havayah - "Ki Sihyenah l'Ish Shtei Nashim." Just like Havayah there is Nisu'in (it says that they bore children to him), also Havayah here is Nisu'in.