Why didn't she get the email?

Wickham didn't write an email to Lalita, but rather to her sister, Lakhi. This can be seen by looking closely at the recipient-adresse of the mail. From the wording of his email, Lakhi had sent him an email before, thus triggering his response. And thus, one might add, violating the rules her parents probably imposed on contact to men. It might be noted that neither Lalita nor Jaya, both of them better behaved than Lakhi, contact Balraj or Wickham, but rather wait on their emails.