Getting DP when on Visit Pass

If her DP gets approved while she is in Singapore on another visa, this can be converted during a visit to the ICA office.
But there is no guarantee that a DP will be approved before expiry of the other visa, or at all.

You mean Do I need to Visit ICA for converting ?
Once her DP gets approved , then there is no necessary if Visit pass/tourist visa right

Please check with ICA, but to my knowledge a visit is necessary to return the white immigration card and take fingerprints/photos.

On her DP approval, MoM will ask her to visit MoM to provide finger print, photo session and verify the documents, if any.

Once it’s done, they will give an auto generated letter which confirms that she has submitted and verified her information. Pending to collect her DP in a week time.

Once she has that letter, then she can stay in Singapore and DO Not need any visit visa.

But, if her DP didn’t approve or didn’t complete the above mandatory formalities within her visit pass days (immigration officer must have stamped in white embarkation card), then she has to either extend her visit visa to additional 30 days (you can apply online using your SingPass) before it expires OR has to leave Singapore.