The suspense is over!
Thank you for the responses. The night before the party, I mentioned the situation to my DH who basically thought I was making a big deal out of nothing and that I should just let her come early. I guess from being tired and stressed about the preparations I decided I would try to give her an out but if she insisted I would just say ok, 30 mins early is alright.
So, that's exactly what happened, she said she didn't what to upset her DD by not going so she'll be there 30 mins early. I know I'm an e-hell failure, I asked for advice and didn't take it.
Anyways, the morning of the party was going decent until it was time for me to go get the balloons aired up at Walmart, it took the better part of an hr so I didn't get back to the party until 15 mins before party was to start. Just an FYI to any kid bday party planners out there. It's .50 cent per balloon at Walmart and $1 everywhere else (grocery stores, dollar stores, etc..). However, if you DO go to Walmart, get there hours early because they were so slow about it and with a bad attitude to boot.
Ok, so by the time I arrived at the party, Snarkles still wasn't there. Her cousin arrived a while later and asked if I got Snarkles' text. I hadn't because I wasn't near my phone but I did read it later. It said "Can't come to party, we'll talk about it later, sorry to be so flaky." Her cousin hands me her own phone for me to read the texts that were sent to her about the matter. It said something like: "Fiance is being needy because he's not feeling good and doesn't want us to leave him to go to the party. We are probably not going out of town to the zoo now either. Pls tell PumpkinSpice I can't come and that I sent her a text."
Party went really well without her. I couldn't ask for a much better outcome. When we left the party I sent a response to her text saying: "It's ok. Sorry you couldn't make it. TTYL" So, there you have it folks.
Now I see she's sitting at her chat waiting for me to get on there and talk to her. I cringe at the thought. I see she didn't go out of town after all.
I know I didn't handle it the best that night by giving in to her but from here on out I'd like to be better. We will see her next Saturday at another girl's party but after that there is no standing plans to be around her.
ETA: I think that one thing I should do is only email her from now on and eliminate the chat altogether which would be a bold move.