D&D Advice?

Okay so a friend is starting in a D&D campaign online and I'm *ridiculously* excited. But I haven't done any sort of tabletop RPG in many many years, and for D&D it's probably been more like 25. Thanks to Critical Role, I've had a long-running refresher course on mechanics, but that doesn't help with character creation. So I have a question.

As I've been thinking about it, I've become enamored of running a glass cannon -- deals lots of damage, but pretty squishy (right now, her CON score is 8). I don't think jumping in with a full-blown mage is a good idea; my original thought was to run an Eldritch Knight (Fighter with a little magic), but then I wondered if an Arcane Trickster (Rogue with a little magic) might work in terms of staying out of the line of fire (ability to hide, disengage, hit hard with sneak attack, etc.). We're starting at Level 5, so she'll already have some magic and other skills.

First, is this idea completely ludicrous? Is Mallory just going to die right off? Especially given that the party has no cleric (we do have a druid).

Second, if I do run with it, which direction makes more sense: fighter or rogue? I can make either work in terms of the personality and backstory I've already developed. (Mallory is a half-elf; she grew up with her elven mother on the outskirts of an elven town, left home young to go adventuring with her aunt Devan -- who is basically the ranger I played in my last D&D campaign :) -- then split off from her when she developed an interest in learning more magic, which is how she ended up in the place where she'll meet the rest of her party.) There's already a fighter in the party, but a very different type of fighter. Still, party balance suggests rogue, but will a rogue deal enough damage to be worth the squish factor?

All thoughts welcome!