<human>: Can you condense the text into three sentences or less?

I posted this a little while ago, posting again in order to get a little more advice. 

I've been officially dating my current girlfriend for a little over a month. We go to the same university and the second semester is just finishing up so we'll be going long-distance for our 2.5 month summer break, (we live in different states), but we've had talks about me flying out to visit her for a week or so.
Anyways, I recently noticed she's been texting an ex-boyfriend from back home fairly regularly- as much as she texts me, potentially more so. She even does this when we are hanging out together, or are out somewhere or on date nights. I asked her about this guy, and she got a bit defensive claiming they were "just friends."
Problem is, I've come to learn through past relationships that being close platonic friends with an ex just seems to cause a lot of problems for the current relationship. Its one thing to be civil and friendly with an ex, maybe checking in from time to time, but texting them almost 24/7, even when you're with your current partner? I find this to be very worrisome and problematic.
Anyways, we are about to go long-distance for about 2.5 months, with a potential week-long visit in between, and her "friendship" with her ex really worries me. I'm not going to be around for most of the summer as I'll be in a different state, but this guy will, and they text all the time; I'm really concerned that she will reconnect with this guy in my absence and I'll be the odd man out.
I realize that our relationship is fairly young, but her constantly texting this guy is a big red flag for me, especially given that she'll be pretty close to him, and away from me, for a couple months.
Should I jump ship now, or am I overreacting? I want to let this situation play out how it will, but if it goes badly I'm worried I'll end up hurt.
<bot>: SO texts her ex 24/7 and claims to be "friends." I'm worried because we'll be long distance for a couple months and this ex will be around.