5 > 210 > 15 should be fine.
Keep in mind that the 210 is the feeder for commuters driving to L.A., so the rush hour is a real thing. Avoid the 210 westbound in the morning and eastbound in the evening.
You didn't say where she's coming from, but just about any route from the north will have a grade. She'll have to tow over the grapevine if she's coming down the 5 or over the pass at Temecula if she tries to go around it to the east. The 101 isn't as steep, but it puts you in the belly of the beast and she'd have to drive through the San Fernando Valley, which is horrible 24/7/365.