I'm basing this answer on your statement that you "Will be paper filing with me signing as POA designee."
Here, I'm assuming that you are paper filing -- rather than electronically filing -- you sister's Form 1040. If this is incorrect, please comment below and I'll respond.
But if it is the case that you're paper-filing your sister's Form 1040, simply attach Form 2848 to the back of her return, and file it with your sister's return -- no Form 8453 would be needed, since that form is only required to be mailed when a taxpayer has filed an electronic return.
If Fresno is where your sister's mailed return should be submitted -- you can verify at the
IRS’ Where
to File Paper Tax Returns With or Without a Payment page-- then that's where her Form 1040, with Form 2848 attached, would be mailed.
Your signature format is fine.
