I want to write this:

As she left the room, Hazel's mobile rang. She picked up...

The first she refers to another character who's just been upset. The second 'she' refers to Hazel.
Am I right in thinking that grammatically, if I were being fastidious that the first 'she' is the subject of the sentence, so technically the second she refers to the woman who's left the room, but actually it's clear that I mean Hazel.

It reads awkwardly to put 'As she left the room, Hazel's mobile rang. Hazel picked up.'

One of the few times I wish English had umpteen cases, like German.

It depends on who is the pov/main character. If it's Hazel then she is the 'she', and you should replace the first 'she' with the character's name.:

As Clara left the room, Hazel's mobile rang. She picked up...

Can you join the sentences together and put:

As she left the room, Hazel's mobile rang which she picked up...'

That implies hazel is leaving the room when her mobile rings.

<Added>

Howabout.

She left the room, tucking her hankie into her bag. Hazel watched her go, wondering if she should offer her a cup of coffee, but just then her mobile rang...

Hard to tell out of context. But Hazel is the last female name mentioned, so I think we might read 'She picke up' as being Hazel. Especially if Hazel is the POV character, so that we are defaulting to 'she' as being Hazel.

If you're leaving the sentences much as they are, I think you've got to make clear with names which one is which. It's very confusing otherwise.

You could resolve the matter with:

As she/Gertrude left the room, Hazel had to answer her mobile...

The 'rang' becomes redundant - it's implied by the 'had to answer' bit.

Chris

Thanks all.

Rosy - your response was what i was hoping I could get away with (yes she's pov chara.)

Naomi, I wondered about a longer version but wanted two things to happen at once so Hazel hadn't time to go after Mrs B or respond to the person Mrs B had been fighting with before getting involved elsewhere. It seemed more pressured held together in the same sentence.

Does naming chara A makes a difference grammatically?

As Mrs Blenkinsopp left the room, Hazel's phone rang. She picked up...


I suppose one would have to be stupid or a pedant not to think it's Hazel who answers her own phone. Maybe that is the best version...



<Added>

crossed with Chris. Good idea Chris.

Do you actually need 'she picked up' at all? If the mobile's rung, and then we hear her say something to someone on the phone, then it's obvious she picked it up.
Eg:

Hazel's mobile rang. 'Gareth! Thank god. Where've you been?'

or:

Hazel's mobile rang. It was Gareth. 'You've got to get here, and quick.'

Susiex

(Thinking about it, do we really say 'picked up' for a mobile? It's weird if we do, when all we're doing is pressing the green button.)

Off topic, I know. Sorry.

We do, Rosie. Just as we say we're dialling a number when actually we're keying it into a keypad. (I love words that change their meanings: etymology is my inner anorak.)

Great idea to cut the line entirely. Why didn't I think of that? Duh. Definitely need more coffee or air today. Not thinking straight.