It’s either… “My question is still pending” …or… “Are you going to answer me?”

For that question I would tell it depend of how the teasing is and how the women is generally (delicate or a rebel in example)

If the girl is close and the teasing is direct, a “Tu vas me répondre?” or
“Alors tu répond quoi?” would sound appropriate, but if it’s a delicate teasing, I would tell that “Est-ce que tu vas me répondre?” would sound better.

It’s my opinion.

A note, others expression could be used too;

“Alors tu répond quoi?”
“Tu es sans voix?”
“Un chat a mangé ta langue?”
“Quand tu vas te décider à parler, j’attends toujours une réponse”
“Est-ce que tu vas te décider?”
…

As in English, a direct question as "vas-tu me répondre" is more direct than an affirmative statement such as "je n’ai pas encore eu de réponse".

You can find equivalent turns of phrases to "my question is still pending" as follows (from most indirect to most direct).

Je n’ai pas encore eu de réponse.

Je n’ai toujours pas eu de réponse. (toujours pas expresses a feeling that it has been taken a bit too long now)

J’aimerais une réponse.

J’attends ta réponse.

Tu ne m’as pas toujours répondu.

Same for "are you going to answer ?", from least pushy to pushiest:

Comptes-tu me répondre ? (forml) / est-ce que tu comptes me répondre ? (neutral) / Tu comptes me répondre (informal) ?

Vas-tu me répondre (formal) / est-ce que tu vas me répondre ? (neutral) / tu vas me répondre ? (informal)

Quand vas-tu te décider à me répondre / quand est-ce que tu vas te décider à me répondre ?

If the woman wants to express a sense of impatience and yet be indirect, she could also simply say:

J’attends…

There are also some humorous turns you could use – but they may not have the flirtatious tone you are looking for, they are rather used in a bantering tone, so that depends on the relationshiip between your characters:

Alors, c’est pour aujourd’hui ou pour demain ?

Tu as perdu ta langue ?

Tu es long à la détente !

note: I feel no difference between genders for using any of those suggestions.

I was told that the “tu vas” variants fit best for close friends or lovers, and “est-ce” was slightly more formal than “tu vas.”

This is correct and you can consider “vas-tu…” also as formal. There is no problem of gender difference.

The answer depends a little, as I see it, on the level of formality of the relashionship ; you can be close friends and yet not treat one another too familiarly and/or carry on the interaction by means of more formal language.

If this relationship, then, is somewhat formal “My question is still pending.” would do.
However, the term “pending” seems not quite proper, rather vague to me in this context: “pending” means “awaiting decision”, “undecided” and there is not really a decision to be made about the question itself but a decision about whether answering it or not; it could be said as well that the answer is pending; that’s why I’d suggest to use instead “My question holds.” or may be better “My question still stands.”. Nevertheless, whichever is found to have the most relevance to you in the end I think that the following translations of the idea will do.

• Ma question tient toujours.
• Je maintiens ma question.

If those two friends are very familiar in their interaction it might be preferable to opt for “Tu vas me répondre ? “, the idea being to ensure that all utterances remain wihin a given language register. However, I do not think using the forms considered first would cause a real clash of registers: they are not specially formal. Moreover, even the more formal “Vas-tu” and “Est-ce que tu…” can be found proper if one wants to communicate the idea of something of an ultimatum (stage directions are then needed for the prononciation: “said intently” for instance).

Pour Are you going to anwser me? je propose simplement:

Tu ne réponds pas?

Et pour My question is still pending je suggère:

J’attends.

Dans un jeu de séduction, les deux phrases prononcées peuvent par exemple être accompagnées de mimiques telles qu’un sourire malicieux.