Should I feel bad about my boyfriend saying yes to being a designated driver to his attractive female coworker?

His single female coworker asked if he could be her designated driver when she went on a booze cruise. He said he is only a backup designated driver and she can only use him if there's no one else. But he still said yes. Should I feel concerned?
Should I feel bad about my boyfriend saying yes to being a designated driver to his attractive female coworker?
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