From Chateau Heartiste: This is bad news. This woman is disrespecting him, no two ways about it. Girlfriends who love you will rarely, if ever, talk about exes or, worse, text exes. Nor will they use exes as clubs to counter your opinions or demean your idiosyncrasies.
The fact that your girlfriend is doing this means one of two things: she’s shit testing you for a jealous reaction, or she’s cheating/thinking about cheating. My guess is that she senses your betaness and is beginning to think she can do better, and this feeling of hers is manifesting in passive-aggressive taunts such as her texting an ex.
Amused mastery is fine for one or two infractions, but continual disloyalty from a bitch, like what she is doing to you, requires more powerful artillery…
Talking about exes is a very female oriented manipulative tactic designed to instigate relationship war, and thus feed her rationalization hamster. “Oh, I was great to him, but then he just started getting all jealous and possessive. So I dumped him. What’s that? Texting exes? I don’t remember doing that. Anyhow, there’s nothing wrong with keeping in touch with old friends. Don’t be a creeper.”
This sort of insidious bullshit is what women do when they want to express disapproval about their man but lack the balls to say so outright. A woman’s coin of the realm is subterfuge and sabotage. They have mastered these arts over millennia to compensate for their weaker physical strength.
PS What the hell are you doing worrying about what a single mom thinks of you? You should be waking up every morning gleefully reminding yourself that she has intrinsically lower value than you. Let this knowledge guide your attitude with her.