I can only tell from experience that she was in love with our younger male Dayo. They where all over eachother all the time. But they only had a few weeks together. But you are right..she should move to a other zoo, to try a new male (but i don't see this happen very soon)
Despite the fact that, as we know, mature & experienced breeding males are usually the best bet for successful mating, especially with inexperienced females, there are some situations where a female prefers a different, less experienced male. I'm not just talking Okapi's here.
At Howletts, one female gorilla, Kabinda(now at Beauval Zoo in France) would not let the breeding silverback Bitam mate her- but she finally became pregnant when Bitam's son 'Biju' also in the group, became fertile....
In the case of this Copenhagen Okapi, she has been tried with several partners but has shown interest with only one. So he could be the best bet for mating with her.