Someone that is jealous of your opposite gender friends is worried about the prospects of infidelity.
She is worried that you have too many opposite gender friends, several of whom are good-looking, making you susceptible to committing infidelity.
There is a possibility that she has been in this situation before.
She had a previous boyfriend who had many attractive female friends.
Her heart was broken when the worst of her fears were realized.
He cheated on her with one of these good-looking female friends, which led to heartbreak and emotional torment.
Since then, she has been cautious about dating men who have too many female friends, especially attractive female friends.
To this end, when she realizes that you are someone who has friends of the opposite gender, she is instantly worried.
It reminds her of her last boyfriend and how he ended up cheating on her.
She is fearful of going through that emotional torment again.
She becomes jealous.
Her jealousy is an instinctive reaction to the threat that these female friends present.
Even if she never dated a guy who ended up cheating on her with one of his good-looking female friends, she is still prone to getting jealous in a situation like this.
Women compare their level of beauty with that of their fellow women.
You have several female friends who are better looking than she is.
This makes her feel threatened that you are more attracted to these women.
This is when she surmises that you chose to date her as a last option.
She falls into the trap of making herself believe that you would much rather date one of your more attractive female friends.
She convinces herself that you settled for her instead.
This means that the moment an opportunity to cheat on her presents itself with one of these attractive female friends, you take it.
This is what she is convincing herself likely happens.
Much of this is triggered by how attractive these female friends are, and how they interact with you.
She has observed how they behave and what they say as you engage with them in person or online.
Being a woman, she knows how she behaves when she likes a guy.
She is sensing similar behavior in how these attractive female friends interact with you.
You don’t notice it.
To you, it’s perfectly normal for one of them to call you a pet name.
There is nothing to it.
If anything, it speaks to how friendly you are with each other.
To her, it’s a sign that she likes you, and it scares her.
She knows that the only person she ever gives these types of pet names to are guys she is romantically interested in.
Yet, there you are, seemingly oblivious to this, believing that the pet name she has given you is based on how fond she is of you as a platonic friend.
This is only one sign that tells her that underneath the so-called platonic exterior of your friendship with this female friend, there is an attraction.