Switching topical flea meds in less than a month?

Hello all, first post here, and I hope you can help. Tried to read through the forums as much as i could for duplicate question, but here goes....and sorry if this is an oft asked question

My cat (Baby) has fleas....really bad. I treated her with on-spot treatment like 3 days ago called PetArmor Plus, which is supposed to be the same as Frontline Plus, but it's  done seemingly nothing. Like, really nothing. Tons of fleas are alive and all over her, and the situation is getting much worse throughout the house. I know you're not supposed to give them too many chemicals, or reapply, etc, but do you think that if I bought advantage and gave it to her it would be bad? I thought that maybe it would be OK if they are DIFFERENT chemicals, but I want to be careful. I'm worried that perhaps I didn't apply the PetArmor correctly - she is a very long haired manx. I don't know what to do bc there are manyyyyy fleas all over her and the house is ...infested. Really don't want to wait a month before treating her again but also obviously do not want to hurt the cat.  Anyway, do you think that I have to bring her to the vet or will they just tell me i have to wait 3 weeks before more doses?

Also doing diatomaceous earth, vacuuming, laundry, etc. Just want to make sure the cat is also being treated. Don't want to wait too long for fleas to multiply, etc.

Would really appreciate an advice about applying different meds

Daniella

I just wrote you a long post about how to bathe her an my stupid laptop which is terribly sensitive deleted it adn overwrote the draft.  I don't have time to go into that kind of detail again but suggest you bathe her with a gentle tear-free shampoo (NOT flea shampoo with any chemicals in it) and then comb out any fleas that survive with a fllea comb (flicking them into a dish of water with some soap in it to break the surface tension) and those fleas will drown.  You can continue to comb out fleas for a few days and she will be better off than she is now.  You SHOULD ask your vet about any interaction between the two medications before tryin the Advantge II (don't use Advantage Multi!  More chemicals than you need and not the right combination for an inside cat anyhow.).  I know Advantage II can be used as often as once a week in severe infestations, so it is very safe.  Both products are technically waterproof so you cannot totally wash out the PetArmor Plus.  I have heard that fleas are getting immune to Frontline also and the PetArmor Plus is not as strong, so it does not surprise me it is not working.  Even Advantage is not as tough as it used to be on them, and I use Advantage II every three weeks now.