Actually, the hearing was about religious freedom, and the woman was denied because anyone who testifies at those things has to be scheduled either 3 or 4 days in advance. The Democrats on the committee had originally scheduled a man to speak, then tried to substitute Sandra Fluke at the last minute. Had they followed the rules and given sufficient notice, she would have been allowed to speak.
If you read my link, Darrell Issa had no problem adding last-minute witnesses favorable to his position. And the hearing certainly involved women's rights very prominently (perhaps even more prominently than it involved religious freedom) so the addition would have made sense.