The only way that you can be refused a spouses visa to the UK is if you do not meet the spouses visa requirements, you have a deportation order against you or the Home Office believe that you have tried in some way to deliberately deceive them but even if this case if you appeal and can demonstrate that not giving you the visa would breach your human rights, you can still get it. They are not allowed to refuse you a visa just because you have herpes if you satisfy all the other requirements. In any event there is nowhere on the VAF 4 form on which you apply for a spouses visa that they ask about medical conditions and so unless you specifically bring it to their attention, there is no way they can know.
It is extremely unlikely that they will pay any attention to your ex-girlfriend, especially if she does this before you have even applied for a visa as they will at that point have no record of you and so will have nowhere to make a note of it.
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