At this age we really want to see 1.5-2 hours for a nap, and preferably 2 hours. But every kid is diff, and some NEVER have 2 hour naps. I think for your LO 1.5 hours (2 sleep cycles) should be your goal, and anything more is gravy!
She's not ready to stretch to 1.5 hours. I know it's tough with such a short A time,b ut it really is a short-lived period. I have a feeling the teeth more than anything else are affecting her sleepiness. If you're seeing 'several' bumps, then she's working hard to poke thru many teeth -- and that's hard work!
I strongly suspect once those teeth actually come in that she'll rapidly extend her A time. I'd let her be for now.
On extending A time, I always went by my son's naps: when his naps started getting short, that told me I needed to lengthen A time by 15 minutes. He was a textbook/touchy, so he was pretty clockwork with needing to extend 15 minutes every 4 weeks, almost to the day.
Now, while teething I had to shorten A time by 15-30 minutes for naps and bedtime or we had awful short naps and NWs/EWs. Sounds like yours may be a bit like that too.
Hang in there! A month from now her A time will probably be in the 2h range and that will improve life immensely. don't wish the time away! As you know with your older child, these months go by SO fast and before you know it they're toddling away on their own 2 feet! She'll lengthen A time eventually -- I'm reasonably sure you won't have the only college kid who has to take naps every 1h15!