Liaison between a form of être and the predicate is categorized as liaison facultative, "optional liaison".

Here’s the Wikipedia article on liaison in French — the French version is, understandably, much better than the English one — where you can see this type is listed as the first kind of liaison facultative.

Both are optional liaisons so the conflicting pronunciations you heard were correct. In casual conversation, I guess most people won’t make them while in a careful or formal situation, there is more chance for people to do it.

The gender of the speaker doesn’t affect in any way these liaisons.

See To what extent are liaisons optional? Can I have some examples?

Je suis allée

I’m a native french speaker and I’d say that we’ll make this liaison everytime. But it wouldn’t be shocking not to say it in this case.

However, if the liaison isn’t done in this sentence, it could be understood as "Je suis hâlé", which is sometimes used for "I’m tanned". Of course there would be no doubt if the complete sentence is "Je suis allé à Bruxelles".

Not making a liaison is usually not a problem in french, but what is considered a mistake in french is to make a liaison when the word start with a letter "h". "Je mange des haricots", "Un gros hélicoptère", "des halos lumineux" : never do the liaison on these ones.

But making the liaisons shows you’ve got a certain level in french language, but you’ve got to know the last letters of your words to make the correct liaison. It’s not trivial as many french words have a last letter which is only pronounced when there’s a liaison.