How did Cersei plan to explain her maidenhead?

[Lord Varys]

18 hours ago, Angel Eyes said:

Cersei's not really the horseback-riding type though.

Cersei disguised herself as Jaime multiple times back as a child. Do you think she did that by wearing gowns and not riding horses?

[Vaith]

2 hours ago, zandru said:

Well, now you're going by Cersei's knowledge, which we should by now realize is a mixture of ignorance, self-serving prejudice, wishful thinking and arrogance. We do know that virginity in high born marriages was of vital importance, because of the laws of inheritance. Verifying, sometimes through a maester's very intrusive examination, was often a requirement so that any offspring would be "legitimate" heirs of the man. If not by a maester's lacivious pre-inspection, then the bloody sheets would be the confirmation.

Cersei is an obtuse megalomaniac, but that doesn't mean that everything she thinks is wrong.

We don't actually have any examples of a woman's hymen regularly being inspected before a wedding. The only inspections we hear about are Margaery's -- after she is accused of adultery (it seems like she wasn't required to be inspected before she married Joffrey & Tommen), and Brienne, after a long and dangerous voyage from Riverrun to King's Landing.

Clearly Cersei made it past the wedding without there being suspicions on her virginity, so either tests are infrequent, maesters are aware of the common inaccuracies, or both.

[Moiraine Sedai]

A broken hymen is no proof of having been with a man.  She can always make up reasons.  Horseback riding.  Messing with the bean in her youth. 

[FictionIsntReal]

3 hours ago, Vaith said:

it seems like she wasn't required to be inspected before she married Joffrey & Tommen

There was political demand for a prompt marriage, so they didn't want to risk the embarrassment of a maester confirming she didn't have one. Margaery's claim (which Cersei doesn't believe) that her marriage was unconsummated is a way to assert that any subsequent pregnancy (as they didn't have time to wait until one was obvious) would be Joffrey's rather than Renly's. And there really wouldn't have been any reason to make sure that Joffrey hadn't bedded her before their wedding, which would simply be embarrassing for everybody and achieve nothing. At the same time, you're likely right that such checks aren't the norm before weddings even if they're not under such special circumstances.

[Endymion I Targaryen]

Cersei explained it when thinking about Margaery. Not all women bleed and some nobles lose their virginity on horseback. If Robert accused her she could provide a maester telling that and probably she had no man around except Jaime (which is normal since no one knows about the twincest). She doesnt recall if Robert noticed the absence of her maidenhead though. Either he was too drunk to notice or she did some trick to show the blood.

IMO it was a stupid risk and she was very lucky.

[Haus Berlin]

Thank you for that question, @Alyn Oakenfist. It got me thinking if this might be a case of "kill two birds with one stone"? So, was Cersei dressed to kill that one night in Eel Alley? Jaime freshly knightened and soon to be married off: not so good. She in love with Rheager who is known to leave his wife, just not for her: worse in comparison.

Jaime, who tends to think about their relationship in the terms of "squirt of seed in Cersei's cunt", excepts one night as especially passionate. Cersei woke him up again and again. This certainly is not the way for a well trained highborn maiden to stay intact for her later marriage, it is more a way to ensure pregnancy. And why would Cersei want that?

 

Over and over again it is highlighted how very much alike Jaime and Rhaegar look. What if Cersei wanted to pretend that the prince she loved loved her back? What if Cersei made use of the Lyanna scandal to claim Rhaegar's unfaithfullness for her own case and serve "his" child as a proof? What may have pleased Rhaegar in look for a third head of the dragon, mocked Robert who then had to look into the faces of three Lannister children.

 

I can't see 15 years old Cersei as a natural seducer who got all that she wanted. I see a girl who doesn't know what drives her love interest and who is full of insecurities fueled by her twin's success. 

 

What Jaime experienced that night maybe never meant him. Cersei was happy to accept marriage even with Robert and as it turned out Jaime was only good enough for her in comparison. Cersei's lie about her true love evolved since Jaime found her painting of Rheagar when they were six.