Penal Code section 273.5 is what's known as a "wobbler" in California - it can be charged as either a felony or a misdemeanor. The police will always arrest you for and book you under the felony, but it's up to the DA to decide what charges (if any) and what level is appropriate.
The first question for you is: Is the DA going to file? I don't know - they will review the entire police report and make their decision from there. If they do file, is it going to be a felony? Doubtful from what you described here.
Even as a misdemeanor, a conviction for this charge can have lasting consequences far beyond going to jail and court. It sounds like you have a good defense and should NOT accept any deal without first discussing the facts with a good criminal defense attorney in your area. Do not speak to anyone about this - no facebook, myspace, texts, emails - nothing. Consult with an attorney in your area as soon as possible to figure out where to go from here.
I do domestic violence cases throughout the SF Bay Area. I have 35 years' criminal litigation experience. I agree with the prior advice not to plead. If you have not yet made your first court appearance, you should hurry and consult an attorney, because there is something he can do to help convince the prosecutor NOT to file any charges against you. The case CAN have long lasting consequences against you, even just the arrest can.
For further info on DV cases you can read these articles on my web site: