Mi abuela le entretiene

Question

Why is this wrong:  Mi abuela le entretiene mucho hacer punto?

Accepted Answer

Hola a todos 
1. A mi abuela le entretiene hacer punto.
You always need "a" in front of the person, the same way you need it for verbs like gustar: A mi abuela le gusta hacer punto/ A mi abuela le aburre hacer punto... We've got an activity being the subject, in the form of an infinitive, the verb matching with that activity (in singular) and the person, who is the Indirect object, hence the "a". Here's a lesson that may help with this. 
2. Mi abuela se entretiene haciendo punto. 
This is a similar sentence meaning that my grandma "gets" entertained when/by doing some knitting. It's using the reflexive verb "entretenerse"; the abuela is the subject and the rest is a phrase telling you "how" she gets entertained (by knitting, use of gerund).  Have a look at this lesson here. 
Saludos y ¡Feliz Año!

Answer

I think it should be:A mi abuela le entretiene mucho hacer punto

Answer

I think David's option is correct, maybe with se instead of le,  but the question remains why is Jonathan's incorrect? Is there some rule to follow?

Answer

According to my dictionaries, the "gerundio" is normally used: "Mi abuela se entretiene mucho haciendo punto"... However, the following sentence is also listed as an illustration: "Pintar me entretiene" - so perhaps [the other] David's suggestion would be acceptable too.

Answer

Estimada Inma,Is the a in front of "abuela" the personal a used for Direct Object nouns or the same as the a from "ir a" or simply a preposition meaning: to, at, on, per, but etc.?