As BillJ said in a comment, it should be "whoever". This is actually a case where the usual rule of thumb that people teach for choosing between "who(ever)" and "whom(ever)" will lead you astray.
Even though nowadays, we usually say "it is him/her" instead of "it is he/she", the latter was considered to be "correct" grammar at one point.
Because of this, "whom" is not used for a predicative noun phrase (at least, not in a finite clause—infinitive and gerund clauses are more tricky).
In other words, "whom(ever)" is not used as the complement of words like "is", "was", "are", "were".
For example, even though we would often say "It's me!" "It's him!" "It's her!", we don't say "Whom is it?" That would be considered incorrect. We say "Who is it."
Your example is similar—in "whoever it is", "whoever" plays the role of the predicative complement of the copula "is". The correct sentence is therefore
I don’t want whoever it is to see that I’m a woman alone.