Chances are that YOU, the client, have wonky boundaries, and she is trying to reinforce strong boundaries. You don't like that, so now you're balking. Its pretty natural.
Honestly, many therapists don't realize how important it is to reinforce these strong boundaries. They have their clients email, text, whatever in between sessions. This creates DEPENDENCY when the goal of therapy is INDEPENDENCY. This is a professional relationship so I think its best to be kept as professional as possible. That means tokens of appreciation are not exchanged and such. I think you fail to realize that this is a paying relationship. She isn't your friend, your neighbor or your priest. It can make her job a LOT harder if you start crossing boundaries that then need to be fixed in the future.
Stop looking at your therapist like she is anyone else in your life. You pay her and she provides you with a service. Boundaries need to be rigid as before you know it, you're uber dependent on this person and can't function at all without her input. Not a good place to be. And honestly, you're lucky that she even allows emailing. Most of my therapists didn't allow that and would only allow texts for appointment changes and such (nothing therapy related). The general idea always thrown at me was that if you couldn't function on your own outside of one or two therapy sessions a week, then you need a higher level of care, ie a day program or hospitalization. It may sound rough, but it is designed to force the client to use their skills in between sessions and learn how to function on their own without having the constant input of the therapist.
I think its sad to see how many people responded saying that your therapist is new or inexperienced. This just goes to show that MANY people out there have had therapists with wonky boundaries.....NOT a good thing!
ETA
You may think its "just a plant" but she doesn't know you. She doesn't know if one day, if that plant will die and you no longer see it in her office that you won't freak out and make it into a "my therapist hates me because she threw my plant away!" kind of issue.
Therapists have to keep universal boundaries across the board for the safety of all. Its sort of like when you go into the hospital and everything is locked up and you say "well that's not an issue for ME!" Well, the reason that many things are they way that they are is because OTHER people can't handle XYZ. So maybe there would be no issue with the plant and your therapist, but there would be issues if she accepted a gift from someone else. I think these across the board rules can confuse some people, but they are there for the safety of all.