How do I (30NB) draw boundaries with phone conversations with my friend (36F)?

Hi folks,

I’ve been friends with this person, let’s call her Sylvia, since my first year at community college and we’ve grown close over the past decade. Sylvia and I are polar opposites though. I’m more introverted and Sylvia is the life of the party. While I prefer written communication such as letters, emails, or texts Sylvia prefers verbal communication such as in person conversations or phone calls and hates texting. This causes a little conflict because our schedules are very different–Sylvia is currently pregnant with her 2nd child and isn’t working a consistent schedule. I work anywhere between 4 days and 6 days because I’m always picking up extra shifts without intending to. So, I’m not able to talk during the day or on my breaks.
On my off days, I’m always doing something around the house such as cleaning (vacuuming, in particular) or cooking that may require some focus. Sylvia will have you on the phone for several hours. Our personal record is 5 hours. It’s mostly Sylvia talking about what’s going on, because it’s always a lot. I love Sylvia but I find talking on the phone for more than 2 hours exhausting due to my job and my personal social battery. How do I draw respectful boundaries, be consistent with them, and be supportivve of Sylvia while she’s going through a hard time? I always feel guilty when I tell her I have to go

TLDR Friends have different social needs. One friend likes to be on the phone for hours while the other doesn’t. Less social friend is struggling with creating boundaries.