Are ululations and welcoming the bride with lit candles permissible at Islamic weddings? Is it permissible for women to dance among themselves a folk dance that is not lewd and without mixing with men?

It is permissible to express joy and happiness with ululations, as long as there is no disobedience to Allah in it. However, if the ululations are in an exciting or seductive tone and are heard by non-mahram men, then it is not permissible, as it falls under the general prohibition of speaking in a seductive manner. But if they are in ordinary tones, without coquetry or excitement, then there is no harm in them, even if they reach the ears of men.

As for receiving the bride with lit candles, there is no harm in it, as long as it is not intended for worship or imitation of disbelievers.