I need your opinion on how to respond to a text...

So I have a friend that I always get into fights and arguments with. She always turns it around and makes me out to be the bad guy/ a-hole. I think we fight so much because there's some sexual tension between us. She's married and of course doesn't want to cheat on her husband. And I have no wish to have or be apart of an extra-marital affair. I have never made a move on her, etc.

Anyway, we will occasionally hang out or go out to dinner together for our cheat meal. Lately we haven't been hanging out a lot, even though I've made time for her and tried to get her to get out of the house to have some fun.
So last weekend I had the weekend off and she had Sunday off. I texted her on Saturday seeing if she wanted to hang out, go shooting, or do something else fun. She said she would be too busy doing things around the house and running errands. Ok, no biggie, we're all busy with day to day chores.

But then Sunday night rolls around and I see on her instagram that she had gone to a golf tournament with this guy and a group of his friends. I'm pretty pissed at this. Then I see on Monday that after the golf tournament they had gone somewhere else together. I don't care that she's hanging out with another friend, I mean we all have multiple friends, what pisses me off is that told me she had chores to do so she can't hang out, and then goes and hangs out and doesn't even include me. Along with that she never texts me first, comes up to me at the gym (it's apparently my job to initiate conversation), etc.

Alllll right so she's too busy doing chores but has time to do all that?? So I said screw it. I'm going to ignore her all week - we see each other at the gym everyday and I always stop by to chit chat.
So today I'm doing abs and she comes over my way and I look away/start doing another set. When she's finished stretching I'm in the middle of a set of crunches, she gives me a little wave and I just kind of nod my head to acknowledge her wave.

Now she just texted me saying, "I would have spoken to you today but my gosh you looked upset so I left you alone. What's wrong?"

What should I respond with? I'm still really upset with her... I can ignore her, text her something curt like "Nothing.", something nonchalant, or explain why I looked mad (because of her) - but the caveat with this response is that I don't really want to explain it, we've been through this type of thing before and I always end up being the **** or she finds no fault of her own - in which case I look like a **** for starting yet another fight.

Any other options?? Opinions?? Help??