While the phonetic similarities are real, the old Norse name of the weekday etymologically goes back to Frig's day, and not Freyja's day.
The actual form of the Norse word is somewhat blurred by a possible early loan from Old Saxon (or some other such west Germanic language) into the attested Norse frjádagʀ. This form is very likely from an unattested old Norse *frīadagʀ before the diphthong, indicated by *-īa- here, changed to -já-. The same change is attested and exemplified in Kíarr > Kjárr 'Caesar', and the source form of the initial *frīa- is backed up by Faroese reflex fríggjadagur, which (due to a Faroese sound change called skerping) must come from an older *-īa- sequence.
This was probably a loan from an unattested Saxon form such as *frīadag (backed up by cognates in Old High German frīatag and Old English frīġedæġ), etymologically sourced from proto-Germanic *frijjōzdagaz 'Frig's day'. The Norse form would have been reflected as *friggjudagʀ, which we cannot find anywhere.
The etymology of the word as 'Freyja's day' is untenable because the only time freyjudagʀ appears is in Old Icelandic, attested only in certain authors and later than frjádagʀ — and can probably be discarded as a poetic or stylistic innovation.
Beyond this, Vanadís as the name of Freyja is only a very ritualised poetic convention (a kenning for skaldic poetry, to be specific) and is not a spoken form. It is quite unlikely that this byname would be used to refer to Freyja when her actual name itself was much, much more commonly used.