Chen Wanrong was picked up by Lin Wanyun, and she had always treated Chen Wanrong as her own daughter; therefore, she did not want to see Chen Wanrong get hurt.
Although she didn't know if Lu Chen would go back on his word, she had no other options now, as both she and Chen Wanrong had been poisoned by Lu Chen's toxins.
Moreover, she had no way to get away from Lu Chen; in this situation, she could only choose to sacrifice herself.
She thought to herself, even if Lu Chen reneged in the end and was unwilling to hand over the antidote, it was alright; she could take advantage of their intimate encounter to search for the antidote to the poison they had been afflicted with.