I'm trying to see whether or not women have said a whole bunch in this thread. For what it's worth, I'll offer a bit of perspective from the dark side.
Flex, you were on a first date with a woman you'd only just met. Mary has been friends with Harriet for who knows how long. At that point in a relationship, it's a question of loyalties. Do you have your friend's back the way you normally do? Or do you tell her she's on her own and go off on your merry way with some guy who could very well end the evening with, "That was great. I'll call you soon." and then doesn't ever call again?
Then, you've let your long-time friend (however weird that friend may be) down for the sake of a few hours with a relative stranger. I can appreciate the balancing the situation required on Mary's part. She wants to think of just herself, and yet, friend.
[Caveat to say that, I also think that half-way decent friend would understand that you're on a first date and do their best not to intrude. Harriet has a whole bunch of points going against her.]
Certainly, the whole thing was annoying [Sorry, Flex, I'd love to be able to say "weird" for you, but in the world of my youth, your scenario only made the "annoying" grade. "Weird" had the potential to end with someone stripped to their underwear, tied to a chair and left in a phone booth on a busy street, late at night. Y'know?] and didn't make the best first impression of Harriet, I think it made a decent first impression of Mary because, if nothing else, you know she's loyal and someone you can count on. That's worth something.
Now, if this situation was, say, six months down the road, and you guys had been seeing each other for some time, and things were pretty solid, and Mary maintained her friend-time with her friends, and her you-time with you, then *something* would need to be done about Harriet and/or the relationship with Mary.
See, Flex, I rather admire younger women today for getting their priorities a bit straighter and not immediately dumping their friends at the curb the moment anything with a different-side opening pants zipper wanders by. Women routinely did that back in the "olden days" and harmed their long-term friendships really badly.
I seem to recall (having waded through this entire thread and noted that you called and left a message but I didn't note the times and dates relative to this point) that you left a message for her. Give her time to respond. I don't always get my texts or phone messages right away. I turn my phone off when I'm busy or involved in something with someone. Sometimes people need to be patient and wait to hear back from me. So give it some time. And when you do hear from her, have concrete plans for some kind of get-together, involving the two of you exclusively (ie: I have reservations for two at such and so restaurant), don't mention Harriet, and see how it goes from there.
If Harriet constantly commandeers Mary's life with drama and bs, and Mary allows that, then, as suggested previously, run.
