Yes, she may. Please also let her have a copy of your L1 extension receipt notice, as a proof that you have applied for extension. She will most likely be given a visa until May 2018 and the immigration at POE will also stamp the same.
But I would suggest that you get your extension approved and let her have the visa stamped. Otherwise, you will have to apply for her L2 extension as soon as she lands or within May 2018.