You are conflating the reports. Trump's financial disclosures are not about campaign expenditures. They are about the candidate's personal finances. Virtually all elected offices have financial disclosure requirements.
Melania had income from speaking engagements, and that income was reported in his financial disclosure statements, that's all and as it should be.
The events that she had paid speaking arrangements were not Trump campaign events (which would be treated as Campaign financial expenditures)- they were some other GOP political group or PAC not coordinated with the campaign.
PAC's can have fundraisers, and they can pay prominent people for speaking engagements...