Neither is Barbara. She's an adult, allowed to make her own decisions, and in that clip, as described by Barbara herself, she clearly was the one initiating everything. With Bruce being so reclusive and "married to the job" that she probably had to literally throw herself at him, probably using MMA techniques to get him to realize she was trying to bone him. And he reluctantly agreed. And it was very likely something that only happened after years of trying to get him into her. I mean come on, Bruce is a poster case for "fear of emotional attachments" That was in fact, exactly why Barbara said she left. He is terrified of making any relationship connections with anyone, for fear of losing them like his parents, and possibly also at least one Robin (depending on the canon of the series in question), so he keeps them at arms length. But Barbs, an ADULT, fully capable of making her own relationship decisions, good and bad, decided to hook up with him.
Sorry but I just can't buy calling someone in college, a "child". This isn't a pedo case, it's not like Bruce walked up to her in the batcave and was like "you know, you'd really make some progress in this vigilante criminal crime fighter business, if you showed up to work showing some more leg sweetheart." Does anyone really think it went down that way? Given how Bruce is always portrayed as far as emotions? Come on. She probably had to set it up like that britney spears parody video, just to get Bruce to realize she was into him.
And like all of his relationships, it goes well for a while, but his alter ego always wins out over stable love life, and so they break up in some manner.