As you are doing a mainlining plant, is it your sides splitting it? If so, do not stem split.
You need to build branches. Something like a Y shape or a bamboo stick, stick, pole etc and split it and brance your 2 main stems from your mainline plant. As the issue will just get worse as she gains more weight
Also, if you are growing in a tent. You can make simple braces from string and holding up weight
The 1st option is best. As if you brace it with string. It'll be hard to move for defols etc. So braced from your soil up to your 2 main stems.