Wordfast is able to check spelling using Word spelling engine
In Wordfast, please select Edit > Preferences. In the dialog window that appears please click Spelling on the left pane:
The screenshot is made in somewhat obsolete version 2.3.0, but the way of configuring spelling check is similar in the subsequent versions.
On the right pane, select Microsoft Office Spellcheck, then press OK. After that, Wordfast will check spelling with Microsoft Word engine.