Does Allay, Eager Admirer Ability give units with deflect more deflect?

Yes, the Deflect keyword from Allay, Eager Admirer stacks with existing Deflect on your other units.

According to Rule 809.2: "If a Unit has Deflect, or has been granted Deflect, and is granted Deflect by an additional source, the Deflect Value of all granted Deflect keywords is summed."

When you have a unit with Deflect (which defaults to Deflect 1 if no value is listed, per Rule 809.1.b.3) and an Allay, Eager Admirer at the same battlefield:

1. The unit has its base Deflect 1.
2. Allay, Eager Admirer grants it an additional Deflect 1.
3. These values are summed to create a total of Deflect 2.

As a result, an opponent must pay 2 Power as a mandatory additional cost to choose that unit with a spell or ability (per Rule 809.1.c).