I have struggled with this one too, but "come" and "arrive" can have different meanings. When saying someone will "come to" a place it normally implies that you yourself are at that place. "Arrive at/in" does not carry this additional meaning. Other times, however, the two words are synonymous, especially when used with regards to time, eg "Summer will come/arrive" "You will come to/arrive at a decision." When translating "llegar" it is best to ask yourself: will there be a difference in meaning if I use "come" or "arrive?" If the answer is yes, then use "arrive." If the answer is no, then use whichever sounds more natural in English. EDIT As an additional note, I believe the usage of "llegar" and "venir" is comparable to our usage of "arrive" and "come," so if you wanted to say "Tomorrow she will come to Paris" you would say "Mañana ella vendrá a París." A native speaker may want to confirm this.
I think to come to and to go to are a little more focused on the process of movement between locations and arrive more focused on the one point of arrival. Of course get to, which is currently the answer shown above sort of covers it all. Get has probably more meanings and uses than most other verbs.
Just a note for non-English speakers: With certain verbs our future tense is often substituted by the present tense when accompanied by a future time reference. Eg "She arrives in Paris tomorrow" is a common way of saying "She will arrive in Paris tomorrow" when we are certain that event will occur.
Interestingly the SpanishDict.com speaker pronounces the two words the other way around: "llegar" with a "y" sound and "ella" with a "j". Maybe it's just a case of say what sounds right to you. I know there is also a lot of regional/international variation with the "ll" sound. Check out: http://www.forvo.com/word/llegar/#es You'll hear the "y" and "j" sounds and also "che".
De nada Susanna. The simple future conjugation is actually one of the easiest to learn because there are very few irregularities and the same ending applies to all verbs, be they -ar -ir or -er verbs. Just take the infinitive and add "é" yo, "ás" tú, "á" usted, él, ella, "emos" nosotros, "án" ustedes, ellos, ellas.
A nice way to remember this is a note from SpanishDict: "The simple future was originally formed by adding haber to an infinitive. (viajar he - travel I must, viajar has - travel you must, viajar ha - travel he must, etc.)." So, if you forget the correct ending just add the correct "haber" form, but replace the "h" with an inflection (which will naturally fall in the right place on the "emos" ending and therefore require no accent mark).
As an added note, Spanish present tense is also used more often than the future tense to express future events. The same usage applies in English. eg ""She arrives in Paris tomorrow"="Mañana ella llega a Paris." This tense can be used in both languages when the future event is a certainty, not a supposition or an intention. I'm not sure why DL doesn't teach this, probably to avoid confusion, but it is my understanding that Spanish uses this form as often as we do.
We just don't normally say She will arrive to Paris in English. She will get to Paris or she will arrive in Paris or She will reach Paris would be the normal English expressions. There is admittedly a somewhat fine line in determining a good translation which is literal enough to be demonstrating whatever Duo is trying to show and still is what one would say in English, but one of the common things you will find is that the preposition used in one language does not match the one used in the other.
Obviously it is more literally will arrive in. But to get to a place is a colloquial expression that means the same thing. It also has no direct translation in Spanish as it is essentially an English idiom. So since it is a common way to express this in English AND it can't be expressed that way in Spanish, this is a valid translation. Whenever the more common English expression has a valid direct translation, Duo rejects it as a translation. But the best rule to check the validity of a translation is to translate it back to the other language. If this exercise had the English sentence Tomorrow she will get to Paris, then Mañana (ella) llegará a París would be the obvious translation.