Female lecturing

1) Is it ok for Yasmin Mogahed to lecture women here for the ROU in Trinidad and Tobago http://www.revivaloftheummah.com/

2) Female lecturers in front of Males without a veil is it allowed?

3) If it is the practise of The speaker normally, should we encourage her to speak to females alone, knowing that her influence would be transferred to the women in the gathering.

4) Some argue that women lecturing men was found in the time of the Sahabah etc. is this a bases that allows this type of action

Please answer with light from Quran, Hadith and Aqwaal of Ulama etc…
Jazakumullah