floored, work advice

I would like some advice on a situation at work. I am pretty young on the office scene and could use some different perspectives-

I share a work space with an office assistant and we are separated by a cubicle wall, our jobs have nothing to do with one another’s. She came over to me out of the blue after lunch last week looked visibly upset and said "I’m going to ask you this because if I don't its going to bother me...did you not answer those phone calls? Because I heard you not answer those phone calls."

I responded to her “huh? Those were hang up calls, there was no one there to answer.” I work a switchboard so I get many calls a day and a lot of them are hang ups/ fax machines/not humans...

She says; "well you are putting me in a position where if someone were to ask me if I thought you were answering the phone or not I would have to say no."

I say “you’re kidding me, you’re being really accusatory and threatening, basing this off of two phone calls you may or may not have heard me answer? Since when is it your responsibility to decipher whether or not I’m doing my job?”

she goes on "I like you, and I’m only telling you this because I don’t want to get you in trouble."

“Ok so you like me that’s why you would go ahead and throw me under the bus if someone were to ask you if you thought I was doing my job, you would say no. That equals, you like me?“

I have never had words with this woman in the time that I have been working here and I’m so confused about why she decided to be suspicious of my duties all of a sudden last week. I’m chalking it up to she was bored because her friend she usually chats with non stop, was out. But now things are very tense at work, I can’t even look her in the eye anymore, I feel betrayed or something. She kept insisting that she was trying to be “helpful” but all I am feeling is hurt that she was accusing me of not doing my job and pissed that she would stick her nose where it doesn’t need to be sticking it. I feel as if she was completely out of line. I would never ever go over to her desk and accuse her of not doing her work. Or rather go over to her desk and say, “you know soandso you are really putting me in a place where if your boss were to ask me [which he wouldn’t ever] how you behave while he is out of the office I would have to say disruptive and chatty.” I’m just really floored that she would be so bold, especially since she doesn’t know what she’s talking about and is def not a contender for ‘the best office assistant ever’ award. When her boss is out of the office she fills her days with searching the internet for alarmist articles about cantaloupe and pushing cupcakes on everyone in the building. How do I move forward with this assuming, careless, obsequious human?