This thread made about as much sense as a box of frogs!!!
As I understand it:
a) You have a friend who used to provide you guys with childcare, but spent most of her time farting about online
b) You made a very vague joke about her basically just using her job as a free internet cafe
c) She gets bizarrely angry and starts screaming at you
d) You apologise a lot, she continues to ignore you and be in a huff
e) You figure "well screw you then" and cut her off.
f) Your husband then tells you he thinks you were being a bit harsh.
g) You want to look at your husband's phone....because you think he has been texting her?
Okay. Firstly I think your friend sounds like she has a screw loose or is hiding a guilty conscience or something. You shouldn't need to grovel over something like that. Then again, maybe it hit a nerve. Who knows. The fact is that you apologised, and sincerely so.
If she can't get over it, then that's her problem really.
It might be that your husband is just annoyed because you two have lost a babysitter, and he doesn't want the hassle of finding a new one. So he wants this to get sorted so things can go back to the status quo. If he wasn't there when she went off on one, then he might just assume that you were exaggerating.
My thoughts are this:
You don't have to support your spouse blindly if you think they are in the wrong. However, you do not side AGAINST your spouse in an argument in front of other people. At worst, if you don't agree with their view, you berate both parties for being ridiculous and tell them to stop it, then you speak to your spouse separately afterwards.
You certainly don't get involved in a personal spat and text the third party telling them you think your spouse is being totally unreasonable and is completely in the wrong. I'm sorry, but you just don't.
Have you asked him why he thinks you are being harsh? Is it possible he misunderstood the situation? Could you not just tell him "I don't want someone in my home - who I am PAYING to be in my home - screaming at me, refusing contact, and not turning up to work with no notice".