Hi,
This is not a "bug". It is happening because your website width is too small. The element doesn't fit in there. The easiest way to solve is to move that "forget password link" from there to below the field.
open this CSS file:
/templates/YOUR_TEMPLATE/html/com_virtuemart/assets/css/flexibleVM2Global.css
scroll to the bottom and include this CSS rule:
.FlexibleForm .FlexibleFormRow a.forgot {position: initial;}
to remove the "or use Checkout as Guest" expression from there, edit the Virtuemart Language INI file, which is located here:
/components/com_virtuemart/language/en-GB/en-GB.com_virtuemart.ini
regards.