I'm no expert but I think you can usually put it either way and the sentence will still make sense, BUT you should put it in the most logical place. In this sentence it makes more sense at the end because you're saying "I respect THEM" so you wouldn't put "a ellas" in the beginning because then it would emphasize them when it shouldn't? But in "A ellas le gusta..." for example, even though you could put "a ellas" at the end, it makes sense to put it in the beginning because the focus of the sentence is really the girls liking something. Maybe I'm just rambling but hopefully that helped you. haha.
Daniel - the las here is not the article "the" but the clitic las required for the Direct Object a ellas. It's a rule to use it when your DO is a Pronoun ("them", in this case).
The a before ellas is the "personal a" which has NO English equivalent, and which is required when the DO is a person/pet animal.
Please try to avoid translating word for word and avoid applying English grammar to understand the Spanish sentence construction. They're different languages and each has its own grammatical rules.
Them is the direct object of respect. The direct objects are los and las. Therefore "Yo las respeto" is correct. If you want to say "I give respect to them" the verb is now "give" and "respect" is the direct object. The sentence in Spanish would be "Les doy respeto." In that case, you would use the indirect object les.
The Spanish personal pronouns are: yo (I), tú (you), usted (you formal), él (he), ella (she), nosotros/nostras (we), ustedes (you plural), ellos/ellas (they)
The Spanish direct object pronouns are: me (me), te (you), lo (him/it), la (her/it), nos (us), los/las (them. formal you)
You can see that your semtence translates as "I respect he." In "I respect him," I is the subject and him is the direct object of the verb respect.
To say I respect him, the sentence should be "(Yo) lo respeto." You probably would not use the yo because it is the only choice with the verb form respeto.