How do I make Siri send text messages to a specific number?
These settings can be harmonized so that no matter how the sender responds, you receive your message on any of your devices including your Mac.
For complete details on setting up Messages for all your devices, see this Apple Support article.
iOS - Settings

Go to Settings in iOS and select Messages
Scroll to the Send &amp; Receive setting and select it (tap)
Here you can add email addresses associated with your Apple ID

Mac Settings

Open Messages app
Select Preferences... from the Messages Menu
Under the Accounts tab, add email addresses where you can be reached at on your Mac

If your phone number is missing:
If your phone number is missing from your Mac Sign out of iMessage and FaceTime on your Mac:

Go to Messages &gt; Preferences &gt; Accounts.
Click iMessage in the left column, then click Sign Out.
Go to FaceTime &gt; Preferences.
Select your Apple ID, then click Sign Out.

Sign back in to iMessage and FaceTime on your Mac:

Go to Messages &gt; Preferences &gt; Accounts. Click iMessage in the left column, then enter your Apple ID and Password to sign in.
Go to FaceTime, then enter your Apple ID and password to sign in.

With these properly set, you should be able to see and respond to messages no matter what account they are sent to.  Siri will not even notice a difference.