Is it permissible for a Muslim woman traveling to perform tayammum if she is unable to perform wudu due to the presence of men at the ablution area, and in order not to miss the prayer time?

The questioner either was unable to perform ablution except by uncovering her 'awrah in front of non-mahram men, in which case her action of resorting to tayammum was correct and her prayer is valid; or she did not exert her effort in obtaining water purification due to ignorance or misinterpretation. In the latter case, it is safer and better to absolve oneself of responsibility by repeating those prayers, and she should be cautious about their number.