Let us remind ourselves of the context of these lines. Hermia and Lysander, having ran off into the woods together so that they can elope, find that night has come and they are tired. Lysander tries to argue that they should sleep side by side, but in the lines you have indicated, Hermia presents an argument as to why they should actually sleep apart from each other. The way that Hermia talks in these lines is designed to dissuade Lysander whilst not trying to offend him. Note the way that these lines begin by flattering Lysander, by saying that he "riddles very prettily." Hermia will not go as far as suggesting that Lysander is actually lying (although this is implied in the second line), but she does reaffirm their two identities as a "virtuous bachelor" and "maid" who must show "human modesty" in their relationships. Hermia is very clearly signalling to Lysander that, although they have ran off together to elope in secret, they are not married yet, and therefore must act in accordance with their status until they are actually married.