If her BF is ignoring her and travels often, then it will actually be harder to get her to leave him (Law of who cares less applies). In this case, I suggest sending her a text saying:
You: "Ok, 7:30 then!".
HB: "What's 7:30?".
You: "Church services, You need some God in your life! LOL".
HB: "LOL" or something in a fun tone.
You: "Haha, actually that text was not meant for you, I am meeting a friend at 7:30...But you do need some God!

"
Then go cold (no replies to any texts)!
Next time you can use recall humor "Find God?" to get a laugh.
Peace...
Ummm yea....because women love being ignored by their boyfriends. Its far more common for a girl to dump a guy who isn't tending to her attentional needs than the other way around. Hey, its not uncommon for women to 'roam' while their guy is away, in fact it happens more often than not. You're also making an assumption that she's more invested, we don't know this as his being away is more a logistical thing then any indication that he's somehow less invested in her. The so-called "Law of who cares less applies" infers that the person who is less invested holds the balance of power in a relationship, we do not know this to be the case.