Potentially losing half of the value of my property/ies

Hi,

I purchased a property 4 years ago and moved in to that property with my defacto partner straight away. We have both lived there since. I understand that would mean she is entitled to half of this property, despite the fact that I have paid every cent of the mortgage myself (no contributions from her at all).

I would like to purchase another property now, but am concerned that I could get myself into a situation where I could potentially lose half of the value of both properties if we happen to split in the future. I have worked very hard in my life to become successful career-wise whilst she is only just beginning. I have put off buying again to avoid this potential issue, but feel I shouldn't. The relationship is all good, but I worry about losing so much of what I have built up over the last 15 years.

My question is, is there anything I can do (apart from a prenup) to avoid potentially losing so much? A trust or anything else? If a trust, am I likely to be (much) worse off tax-wise? Pros/cons?

I'm on the highest tax bracket and my partner is on the lowest so, a) it would make it far more tax-effective to have it 100% under my name which will be difficult for her to accept; and b) I will be paying the whole thing anyway.

I feel bad writing this, but want to make sure I protect myself. Any help would be much appreciated. Alternatively, anywhere I can get free advice?

Thank you!