Before you read this, please note I am no expert tulpamancer ,and I don't even have a fully formed one myself. I, however, have a ton of experience with wonderlands and mindscapes due to having messed with them since I was a child

I've rarely heard of hostile tulpas, and when they do exist it's because you yourself were quite mean/ignoring to them.

I hypothesize since they survive and gain more sentience and suchlike by forcing and attention being given to them, this hostile prototulpa is trying to make you force her by making her stay in your mind and that you're at least somewhat paying attention to her. Paying any attention to something /does/ force it, however weak said forcing is, and they do dissipate/die when ignored and suchlike for a sufficiently long time. Could be simple will to continue existing.

I reccommend reasoning with it "What do you want?", maybe nonverbally if you have to. Not that you should let it totally get it's way with you and possibly any other constructs.

I've had troubles with unwanted constructs in my mind before, mainly because of my very, very chaotic mind that tends to do things I don't want it to and "run off without me".

However, I don't believe the things I do against such constructs would work on a full on tulpa, even a proto tulpa. But I do recommend completely ignoring unwanted things. By giving attention to something, you however weakly force it, if you admit this or not. Another issue is that she could get some of your other prototulpas to force her, even if it's weaker

You can make any mind construct go away, even if's temporary, by doing hostile things back, like blowing the avatar away into space, vaporizing the avatar, etc.

However, ignoring unwanted constructs and letting thhem dissipate is the best idea to combat anything. Blocking a mind voice shouldn't be /too/ hard, and nooby tulpamancers like me accidentally block out their tulpa's voice all the time. If this hostile tulpa's fucking with you in your mindscape you can very easily force them to go away by blowing them away, etc.

However, it might also be worth it to just deal with it and take care of all of these tulpas, as long as it isn't too bad, you definately should feel bad about being forced to hurt or dissipate any mind construct unless it's something like one of hte chaotic mind constructs like the strange wo lves that always attack me and my prototulpa in my mindscape now and then.

No matter how hard a mind construct pushes at you, remember that you can push twice as hard.