If this was indeed an investigation passing usual legal requirements with the intent to build a case against her, I'd imagine that any responsible investigator would at the very least choose to do that as well. If they repeatedly searched her at the border (thus essentially abusing an avenue which had its legal hurdles significantly reduced for the ostensible sake of national security and being able to deal with external threats that the internal legal system had no time and opportunity to handle through regular channels) but did not choose to obtain a warrant or otherwise start a legal process that comes with the normal set of safeguards, I'd say that strongly seems to indicate they did not have enough of a case against her - or, in other words, that an investigation was perpetuated which according to traditional legal standards should have been discontinued.

Now, of course you may argue for the traditional standards/safeguards themselves to be weakened (e.g. by saying that while searches of one's home should remain subject to the same legal restrictions, certain parts of the government now also shall have the privilege to conduct some sort of "preliminary searches" which do not come with the usual safeguards to arbitary ends which might include a more formal investigation being started, at their full discretion), but this is not how I usually see this debate being framed.