Squiggle, I've only been here for a little bit, but I can tell you ask the best questions.

This question is fantastic. The premise would make a dynamite book or film. I've even thought about it before because I'm often getting caught up in bizarre plots in my own little world. Doesn't matter that I wouldn't want this to happen, it's just fun to use the imagination.

I'm going to interpret the scenario as we both keep our own bodies, but I'm sure our ages would have to reverse or equalize (I'm in my twenties, she's in her fifties). Maybe we're both 35, here. I also interpreted the prompt to mean that the roles have been reversed since the onset of therapy, rather than having it just miraculously happen one day, Freaky Friday style.

I would probably have a much more affectionate style than she does, because I am a terribly affectionate (and I mean terribly. I rarely show it but it's like this debilitating, blazing furnace inside me with people I really love) person and she is not. I would definitely have to curb it, somewhat. I would, however, try to preserve the bits of her style that I find valuable. You point out some great guiding questions (prepare for TLDR):

Would I allow her to sit close by me? Perhaps. I think I would generally maintain distance of at least four feet, having her sit on a couch and me in a chair, but I would sit next to her if showing her something important.
Hold my hand? Definitely, if she wanted to. Which, judging by her generally reserved and logical demeanor, I doubt would happen.
Hug me? Yes, on occasion.
Would I wipe her tears when she cried? I don't think so. Not that I think it violates boundaries or is odd, but I know if she ever tried to wipe my tears away while I was crying, as a patient, I would freak out. I always hide my face when I cry; I don't want anyone to touch or look at me when it happens. And I have a hunch she wouldn't invite this. If she seemed especially distraught and shattered, I might ask if I could hug her, or hand her a tissue.
Would I allow her to email me? Yes, but I wouldn't respond in length to emails so long as to constitute their own actual session.
Text me? My T doesn't have her patients text her (she only gives out the number to her office phone), so the concept seems alien and overboard to me even though I realize many Ts do let their patients text them. I think I would stick to the office phone.
Call me between sessions? Only in emergencies. This is her policy, as well.
Would I encourage her to look at me when she is talking? No. She can look wherever she wants.
Would I make eye contact with her at all times? Not so much as to make someone feel pressured or uncomfortable. Do therapists out there actually try to do this? At all times?
How would I handle transference if she brought that up? I would try to help her explore the feelings as far as possible. I think that the way you help people cope and explore feelings depends, to an extent, on that person's temperament. I find that sensitive, emotional people want to be able to focus on the other person and connect to a gentle voice. Traditional, pragmatic people want to focus on the role and authority of the therapist. The more cerebral folks do well when you help them understand the workings of what is happening. She is highly intellectual and rational, so I would explain some dynamics to her after helping her explore the feelings, being careful to never tell her outright what she herself is feeling (that's her job to figure out).
What about erotic transference? I would explain that love naturally arises because of the intimacy of psychotherapy, but that there are boundaries necessary to keeping the love at its purest and most healing. I would also explain my ethical duty as the therapist. I already struggle with this as a patient, so I actually sort of anticipate disaster if she were to reciprocate. Terrible.
Sexual issues? I think with sexual issues it's important to maintain a nonreactive, neutral tone that neither praises nor condemns: their sexuality just is, and it's simply important that they don't hurt themselves or others according to the value systems of those involved. Obviously, if she were taken advantage of, it would be time to display compassion for her and anger at the perpetrator. I've never talked with my T about sex, so I actually have no template to work off of, here...
Would I be open to anything she wanted to talk about? Absolutely, unless she were asking personal questions about me, in which case I would have to turn the question back towards something that pertains to her.
Would anything be off limits? Calling me at home. Romance, obviously. Meeting outside the office except in perhaps the strangest of circumstances (not even sure what those would be).
What if she said something that hurt my feelings? I think as a therapist it's actually important to be able to remain unfazed in the face of insults, because it's valuable to recognize and handle negative transference. Furthermore, I wouldn't want her to have to edit herself on my behalf unnecessarily.
What if she came in and stared at the walls and wouldn't talk? I would remain silent as well until she spoke. The silence could stretch for minutes. If it got to be like five minutes or more, I might ask her "what's going on?" Sometimes I remain quiet for stretches of time, and my T never interrupts it. This is because she can see cogs turning, though, and she knows I'm formulating thoughts to speak out loud in a number of minutes. I might ask her if she needs help talking, in which case I would do that.

All of that really does make you realize how rigorous and complicated the training must be for a therapist.
As things are now, with me as a patient and her as a therapist, she's cool and taciturn, and sometimes I'm the one to make her laugh or bring her out of her shell throughout the dialogue. Once I did a playful but mocking imitation of her and I've never seen her laugh so hard. I have a feeling this would still be the case if she were the patient, and I would just have more power to do so.

Also that office would undergo some radical redecoration.