Here are some questions that you can ask, as a potential employee, to gauge the friendliness of a work environment to women or other marginalized people.
- what does your career ladder look like?
- what did the career progression look like for the last woman who held a position like this one?
- how many women have been there for over 2 years?
- how much mobility is there between teams?
- what are community meetups that people from the company participate in?
- how many people are entry/mid/late career?
In the United States, if there is HR, you can have a HIPAA protected conversation about benefits that they are legally not allowed to share with unauthorized parties. More on this at the HRC site - the information there is specific to asking about gender-identity-related healthcare, but the advice should generalize. There's also the Microactivism Wiki for information specifically about trans-inclusive healthcare coverage here.